Impact of Tax Reforms on Revenue Performance of Federal Inland Revenue Service of Nigeria

Impact of Tax Reforms on Revenue Performance of Federal Inland Revenue Service of Nigeria

Naburgi Musa Mohammed, Danjuma Chamba

Department of Accounting, Faculty of Administration Nasarawa State University, Keffi. Nigeria.

DOI: https://dx.doi.org/10.47772/IJRISS.2025.905000403

Received: 20 April 2025; Accepted: 24 April 2025; Published: 19 June 2025

ABSTRACT

Governments globally face the ongoing challenge of mobilizing sufficient resources to foster economic growth, development, and sustainability. To address this, taxation and tax administration have emerged as vital elements in shaping economic policies. The objective of the study is to examine the impact of tax reforms on the revenue performance of the Federal Inland Revenue Service of Nigeria. This study employs an ex-post facto research design, utilizing secondary data to draw comparisons between the revenue performance of the FIRS in Nigeria before and after the tax reforms. Data was sourced from FIRS to evaluate revenue performance in two distinct periods: before the reforms (1991-2006) and after the reforms (2007-2023). Given the time series nature of the data, a t-test is used to determine if there is a significant difference between the means of the two periods. The t-test evaluates whether the means of the two-time frames are statistically different from each other.  The study’s statistically significant difference between pre-and post-reform revenue levels provides strong evidence that the 2007 reforms had a meaningful impact on the performance of FIRS in revenue collection. The reforms appear to have improved efficiency and tax compliance, making a case for the positive role of systematic tax administration reforms in enhancing fiscal sustainability the findings from this study provide strong evidence that the 2007 reforms positively impacted FIRS’s revenue collection performance in Nigeria. Based on the study findings, it was recommended Expanding digital and automated systems within tax administration can improve compliance and minimize revenue leakages. Enhanced data management and automated processing can reduce errors and increase collection efficiency. Increasing public understanding of tax obligations and the benefits of compliance is crucial for further improving revenue performance.

Keywords: Tax Reforms on Revenue Performance of Federal Inland Revenue Service

INTRODUCTION

Governments globally face the ongoing challenge of mobilizing sufficient resources to foster economic growth, development, and sustainability. To address this, taxation and tax administration have emerged as vital elements in shaping economic policies. Despite significant attention in these areas, effective and sustainable solutions to the complex issues of tax administration are still lacking. The 2019 World Bank Report highlights a steady decline in global revenue performance since 2004, pointing to indicators like Total Tax Revenue & Contribution Rate (TTRCR), the time required to comply with tax regulations, and the number of tax payments as evidence of this trend. This decline is mainly attributed to poor tax administration. Developing nations, in particular, are struggling to meet the Millennium Development Goals (MDGs) benchmark of generating at least 20% of their Gross Domestic Product (GDP) tax revenue. (Adegbie, & Fakile, 2019).

Many Asian, Latin American, and sub-Saharan African countries fall short of this threshold, with revenue mobilization below 17% of GDP. This revenue gap hinders their capacity to finance essential public projects and invest in infrastructure, healthcare, education, and poverty alleviation programs. Consequently, this inability to mobilize adequate resources not only limits economic development but also worsens poverty levels, as governments are left with fewer resources to meet the needs of their citizens and foster sustainable growth (Afolayan, & Okoli, 2020)). The global decline in tax revenue generation underscores the urgency for countries to reform their tax administration systems. Strengthening these systems could enhance resource mobilization, allowing governments to better fund development projects and improve the economic well-being of their populations.

In response, there is now a stronger global emphasis on taxation and tax reforms (Akhor, & Ekundayo, 2020). In Nigeria, key reforms were driven by strategic initiatives, including the enactment of the Federal Inland Revenue Service (Establishment) Act of 2007, which provided the FIRS with both administrative and financial independence. These efforts also involved the re-engineering and automation of essential processes like human resources, finance, and procurement, establishing a solid organizational framework, staffing with specialized roles, enhancing taxpayer education, and revamping and automating tax administration systems. These reforms represent a pivotal moment in Nigeria’s tax administration history. Previously, the tax system was marked by excessive complexity, limited revenue generation, inefficient management, and redundant taxes that often served more as inconveniences than actual revenue sources (Alli, 2019, Ibrahim, & Musa, 2022   Ibrahim, & Musa, 2022, Ibrahim, et al., 2022, Moses, et al 2022, Moses, et al., 2018, Ejura, et al. 2023, Oginni, et al.2014)

Despite these reforms, Nigeria continues to lag significantly behind its leading regional counterparts regarding revenue efficiency and tax administration performance (World Bank, 2020). While Tunisia, Morocco, and South Africa have tax-to-GDP ratios of 31%, 28%, and 26%, respectively, Nigeria stands at a modest 6%, well below the African average of 17%. Moreover, there is limited current empirical research evaluating the reforms’ effects on revenue performance. This study aims to analyze the reforms’ impact on FIRS tax revenue, offering valuable insights for policymakers, stakeholders, and researchers, while filling the gap in the existing literature. It hypothesizes no significant difference in FIRS revenue performance before and after the reforms. The study spans 34 years (1990 to 2023), divided equally to examine revenue collection across the 17 years preceding and following the reforms. The main objective is to examine the impact of tax reforms on revenue performance of federal Inland Revenue service of Nigeria while the specific are to

1. Examine the impact of pre post tax reforms on revenue performance of federal Inland Revenue service of Nigeria and
2. Examine the impact of post-tax reforms on revenue performance of federal Inland Revenue service of Nigeria

Based on the specific objectives, the study formulated the following null hypotheses for testing.

H_O1:    Pre post tax reforms have no significant impact on revenue performance of federal Inland Revenue service of Nigeria and

H_O2: There is no significant impact of post-tax reforms on revenue performance of federal Inland Revenue service of Nigeria

LITERATURE REVIEW AND THEORETICAL FRAMEWORK

Conceptual Review

A famous quote often attributed to Benjamin Franklin holds that three things in life are certain: death, taxes, and tax reform. Nearly every government revises its tax system frequently, whether annually or at other intervals. For a government to fulfill its core functions effectively, it must secure adequate revenue through taxes and/or international transfers from businesses and individuals (Anyafo, 2017). Anyanwu, (1997), argues that tax revenue might inversely affect voters’ inclination to hold their government accountable. Apere, and Durojaiye, (2019). defines government revenue as all funds, including taxes and fees, received from external sources. Government revenue is further divided into tax revenue and non-tax revenue. The term “tax revenue” is understood differently among scholars. While some interpret it legally, based on judicial rulings, others provide more general definitions. The Oxford Advanced Learner’s Dictionary describes tax revenue as “money that has to be paid to the government so that it can pay for public services.” In contrast, Black’s Law Dictionary defines it as “a monetary charge imposed by government on persons, entities, or properties levied to yield public revenue.” According to Ariyo, (2018), tax revenue refers to income collected by the government within its jurisdiction for the sole purpose of funding public goods and services. In summary, tax revenue is a mandatory levy by a sovereign authority on the income, profits, goods, services, or property of individuals, corporations, trusts, and settlements.

Regarding revenue performance, scholars have differing interpretations of its meaning and measurement. Since the mid-20th century, many researchers have applied econometric methods to assess the potential for taxation and the degree to which tax authorities tap into this potential. This analysis introduced two central concepts in taxation studies: tax capacity and tax effort. Tax capacity refers to the theoretical ability of a tax authority to generate revenue for public finances based on the existing tax base, while tax effort indicates the extent to which a region or government effectively collects tax relative to its taxable resources Asaolu, et al.  (2015).

Scholars have identified various factors influencing tax revenue performance, though they do not universally agree on these determinants. Attali, et al (2018).  defines revenue performance as the level of commitment by national or subnational governments to revenue collection, based on available revenue instruments and tax bases. Azubuike, (2020). , however, equates revenue performance with tax capacity and tax effort and defines tax revenue as the total tax collected within a given year. In this study, revenue performance represents the total tax revenue (from both oil and non-oil sources) generated by FIRS in any given fiscal year.

Tax reform is a continuous stream of technical modifications to laws and procedures that reflect specific country circumstances. It has been argued that developing countries cannot achieve sustainable economic growth and development and substantial reduction in poverty without mobilizing domestic resources through taxation (Chigbu, and Njoku, 2020). However, the capacity of developing countries to raise taxes and increase tax revenue is limited by several challenges which include: corruption and lack of transparency; weak tax administration institutions and policy inconsistencies; the prevalence of waivers; the existence of informal sectors (shadow economy); and the outflow of funds to tax havens.

Concept of Tax Reforms in Nigeria

Tax reform refers to the systematic restructuring of tax policies, laws, and administration to enhance revenue generation, improve efficiency, and promote economic growth (Ariyo, 1997). In Nigeria, tax reforms have been driven by the need to address revenue leakages, broaden the tax base, and ensure compliance with international standards. The 2024 Nigeria Tax Reform Bill represents the latest effort to streamline the country’s tax system and enhance fiscal sustainability (Okonjo-Iweala, 2024).

Nigeria’s over-reliance on oil revenues has necessitated the diversification of government income through improved tax collection (Okafor, 2012). The establishment of the Nigeria Revenue Service (NRS) under the proposed Tax Administration Bill seeks to centralize tax collection and reduce bureaucratic inefficiencies (WTS Global, 2024). Reforms aim to ensure a fair tax system by broadening the tax base and eliminating loopholes exploited by corporations and high-net-worth individuals (Ajakaiye & Olaniyan, 2023). The Nigeria Tax Bill 2024 consolidates various tax laws into a single, harmonized framework to simplify tax compliance and administration (Guardian Nigeria, 2024). This is expected to reduce the complexity that has historically led to tax evasion and avoidance (Okonjo-Iweala, 2024). The bill aims to enhance efficiency by reducing bureaucratic bottlenecks and introducing digital solutions for tax filing and collection (Okay.ng, 2024). According to Adebayo (2023), digital tax platforms can significantly reduce compliance costs and increase voluntary tax compliance. Tax reforms in Nigeria have evolved to address the country’s fiscal challenges, with the 2024 Tax Reform Bill marking a significant step toward modernization. While these reforms promise increased revenue and economic growth, their success depends on effective implementation, transparency, and taxpayer cooperation. Continuous policy adjustments and stakeholder engagement will be essential to achieving a sustainable and equitable tax system.

Concept Revenue Performance

Tax reform refers to the systematic restructuring of tax policies, laws, and administration to enhance revenue generation, improve efficiency, and promote economic growth (Ariyo, 1997). In Nigeria, tax reforms have been driven by the need to address revenue leakages, broaden the tax base, and ensure compliance with international standards. The 2024 Nigeria Tax Reform Bill represents the latest effort to streamline the country’s tax system and enhance fiscal sustainability (Okonjo-Iweala, 2024). Tax reforms is revenue performance, which measures how effectively a country mobilizes tax revenue relative to its economic capacity. In Nigeria, tax revenue as a percentage of GDP remains significantly lower than the African average, highlighting the need for continuous reform efforts (Ajakaiye & Olaniyan, 2023).

Optimal Tax Theory

Optimal Tax Theory (OTT) is a framework that seeks to determine the most efficient and equitable way to structure a tax system while minimizing economic distortions. The theory was pioneered by James A. Mirrlees in (1971), who provided a mathematical model for designing an optimal income tax system that balances revenue generation with economic incentives. Mirrlees later won the Nobel Prize in Economics in 1996 for his contributions to the theory of taxation and incentives in the presence of asymmetric information (Mirrlees, 1971).

Basic Assumptions of Optimal Tax Theory is that People vary in their earning abilities and work-leisure preferences. The government must design a tax system that accounts for these differences without discouraging productive economic activity. A progressive tax system (where higher earners pay a larger share) can improve equity but may also reduce incentives to work and invest, thus affecting overall economic efficiency (Mirrlees, 1971). Taxes should be structured to minimize distortions in economic behavior, such as excessive tax avoidance, reduced labor supply, or decreased investment. Mirrlees’ model suggests that marginal tax rates should be designed in a way that maximizes social welfare while ensuring sufficient government revenue. A progressive, nonlinear income tax structure is preferred over a lump-sum tax because it accounts for income distribution and individual incentives.

Despite its theoretical significance, OTT has faced several criticisms such as Real-world tax systems involve political constraints, administrative costs, and enforcement challenges that the theory does not fully address (Saez, 2001). The theory assumes that individuals respond rationally to tax incentives, but behavioral economics suggests that people may not always act in their best financial interests (Thaler & Sunstein, 2008). In developing economies like Nigeria, a significant portion of the economy operates informally, making tax collection difficult and reducing the effectiveness of optimal tax models (Besley & Persson, 2013). While OTT suggests a theoretically optimal taxation structure, political and institutional constraints often prevent governments from implementing efficient and equitable tax policies (Acemoglu & Robinson, 2012).

Several studies have applied OTT to analyze taxation policies across different economies. Saez (2001) expanded on Mirrlees’ work by incorporating empirical data and suggesting that marginal tax rates for high-income earners should be lower than previously thought to encourage productivity. Diamond and Saez (2011) provided empirical evidence supporting progressive taxation, arguing that top earners can bear higher marginal tax rates without significantly affecting economic output. Besley and Persson (2013) Applied OTT in developing economies, highlighting how weak institutions and a large informal sector limit tax efficiency in countries like Nigeria. Ariyo (1997) – Tax Productivity in Nigeria examined the efficiency of Nigeria’s tax system and suggested that optimal tax design should focus on broadening the tax base rather than increasing tax rates. Okafor (2012) Used OTT to analyze the impact of tax policy on Nigeria’s economic growth, finding that inefficient tax administration hinders optimal revenue generation.

Optimal Tax Theory provides a crucial framework for designing efficient and equitable tax systems. While its assumptions about economic rationality and administrative feasibility have been challenged, it remains a foundational tool in tax policy design. In Nigeria, applying OTT requires considering the informal sector, administrative constraints, and enforcement challenges to create a system that maximizes both revenue generation and economic growth.

Empirical Review

Scholarly and practitioner literature on tax reform highlights that enhancing a tax system’s effectiveness is a complex, context-dependent challenge. There is no straightforward solution. A joint report by the IMF, et al (2021) emphasizes that building a robust fiscal capacity is not a matter of simple, quick fixes; however, with sustained political will, meaningful reforms are attainable and can yield substantial success. In this regard, analyzing the political dynamics, particularly friction, and opposition to reforms, is essential to mitigate tensions that could hinder policy goals especially from elites who might face increased tax liabilities.

Yahaya (2024) provides an insightful examination of the impact of the 2007 tax reforms on the revenue performance of the Federal Inland Revenue Service (FIRS) in Nigeria. The study employs an ex-post facto research design, utilizing secondary data spanning 24 years (1995–2018) and a dependent sample t-test to compare revenue performance before and after the reform. The findings indicate that the tax reform led to a statistically significant increase in revenue collection post-2007, reinforcing the need for sustained tax policy improvements. However, the study has notable gaps that warrant further exploration. Yahaya (2024) primarily focuses on revenue performance but does not assess tax compliance rates, administrative efficiency, or the impact on economic growth. A more comprehensive evaluation incorporating these factors would provide a holistic understanding of the reform’s effectiveness. The study attributes increased revenue solely to tax reforms, without accounting for macroeconomic factors, such as changes in oil prices, GDP growth, inflation, and exchange rate fluctuations, which could have also influenced revenue performance during the period under review.

Maurir and John, (2023) examine the effect of tax reform on revenue generation in Nigeria. The study adopts the Ex-post facto method of research design with time series data covering a period of thirty-one (31) years from 1986 to 2017. Data were obtained from the CBN statistical bulletin and National Bureau of Statistics annual reports for analysis. The tax reforms were proxied by Companies’ Income Tax (CIT), value-added tax (VAT), and Petroleum Profits Tax (PPT), while the revenue generation was proxied by total federally collected revenue. The study adopts descriptive statistics, Augmented Dickey fuller unit root test, ordinary least square (OLS) regressions, heteroskedasticity test, and Variance Inflation Factor for analysis. The study found that tax reforms have a positive but statistically significant effect on revenue generation in Nigeria. It is therefore concluded that the taxes have an inverse relationship with revenue generation in Nigeria. The study, therefore, recommends that companies’ income tax, value-added tax, and petroleum profits tax should be reviewed in such a way that it will tackle the hydra-headed monster of multiple taxations and promote accountability and transparency in government business to restore the confidence of the tax payer in the tax system. By addressing these research gaps, future studies can provide a more comprehensive and policy-relevant understanding of tax reforms in Nigeria and their role in sustainable revenue mobilization.

Udezo and Ven. (2022) investigated the effect of tax reforms on revenue performance in Nigeria using time series data from 1991 to 2018. In order to determine the effect of tax reforms on revenue performance in Nigeria, tax reforms were measured by reform in Petroleum Profit Tax (PPT), reform in Company Income Tax (CIT), reform in Value Added Tax (VAT), and reform in Personal Income Tax (PIT) while revenue performance, on the other hand, was represented by total federal collection revenue. Four hypotheses were formulated to guide the investigation and the statistical test of parameter estimates was conducted using descriptive statistics, Augmented Dickey-Fuller (ADF) statistics, Cointegration test, and multiple regression model analysis operated with E-view 8. Ex-post fact research design was adopted and data for the study were obtained from the National Bureau of Statistics, Central Bank of Nigeria (CBN) statistical Bulleting, and Federal Inland Revenue Service (FIRS). The regression result showed that reforms in Value Added Tax (VAT), Personal Income Tax (PIT), and Petroleum Profit Tax (PPT) have significant positive effects on revenue performance. Reform in Company Income Tax (CIT) has a positive but insignificant effect on revenue performance in Nigeria with data spanning from 1991-2018 at a 0.05 level of significance. Based on this, the study concludes that tax reforms have a significant effect on revenue performance in Nigeria, there is a need for further study to validate the findings

METHODOLOGY

This study employs an ex-post facto research design, utilizing secondary data to draw comparisons between the revenue performance of the FIRS in Nigeria before and after the tax reforms. Data was sourced from FIRS to evaluate revenue performance in two distinct periods: before the reforms (1991-2006) and after the reforms (2007-2023). Given the time series nature of the data, a t-test is used to determine if there is a significant difference between the means of the two periods. The t-test evaluates whether the means of the two-time frames are statistically different from each other. It is a robust tool suitable for parametric and normally distributed data and is frequently employed in inferential research. By applying the t-test, this study aims to achieve its primary objective of comparing the mean revenue performance before and after the tax reforms of FIRS in Nigeria. The use of the t-test is particularly fitting due to the small sample sizes for both periods, allowing the researcher to discern whether any observed differences between the two conditions result from genuine changes or simply from random fluctuations over time. Successful tax reform is considered to have met its objectives if it significantly enhances the efficiency of the tax system and increases revenue generation in Nigeria. This, in turn, is expected to improve social welfare, reduce poverty, diminish inequality, and promote greater equity within the society.

Data Presentation Analysis

The results of the various statistical analyses are presented in this section.

Table 1. Data Presentation

Source: Compiled by the Author from FIRS

Table 2: Summarizing the Paired Sample Statistics

Paired Sample Statistics is typically used to compare two sets of related measurements—specifically, it assesses whether there is a statistically significant difference between paired observations, like measurements taken from the same subject at different times, or from matched pairs of subjects. This technique is often applied in pre-test/post-test studies, repeated measurements, or when dealing with two different conditions within the same group

Table 2: Paired Sample Statistics Paired Sample Statistics

Table 2 highlights the mean revenues before and after the reforms, along with the t-test results, supporting the significant difference in revenue performance between the two periods. The paired sample t-test comparing the pre-reform revenue (1991-2006) and post-reform revenue (2007-2023) reveals a statistically significant difference between the two periods, with a t-statistic of 3.40 and a p-value of 0.0052. This p-value is well below the common significance level of 0.05, allowing us to conclude with confidence that the observed difference in revenue performance is not due to chance.

Revenue Increase Post-Reform. The mean revenue during the post-reform period (2,732.86) is significantly higher than the pre-reform period (77,050.21). This suggests that the reforms introduced in 2007, such as granting FIRS financial and administrative autonomy, automating processes, and enhancing taxpayer education, may have positively influenced revenue generation. Impact of Reforms. The substantial increase in revenue after the reforms indicates that the changes likely improved the efficiency and effectiveness of tax collection by FIRS. The shift towards a more autonomous and modernized tax administration could have helped streamline revenue collection, reduced bottlenecks, and enhanced compliance, thus boosting revenue performance.

Table 3: Paired Sample T-Test Summarizing the Paired Sample T-Test Results

Table 3 illustrates the average revenues before and after the 2007 reforms, with the t-statistic and p-value indicating a statistically significant difference in revenue performance across the two periods. ​​ The paired sample t-test results comparing pre-reform (1994-2006) and post-reform (2007-2023) revenues for FIRS reveal a statistically significant difference in revenue generation following the tax reforms introduced in 2007. The analysis shows Significant Revenue Improvement Post-Reform. The average revenue for the pre-reform period was 77,050.21, while the average revenue post-reform dropped significantly to 2,732.86. The t-statistic of 3.40 and the p-value of 0.0052 indicate a statistically significant increase in revenue generation in the post-reform period, with the p-value falling well below the typical significance threshold of 0.05. Implications of the 2007 Reforms. This substantial revenue increase following the reforms suggests that changes introduced in 2007 likely led to improvements in tax collection efficiency and revenue generation.

DISCUSSION OF FINDINGS

The paired sample t-test results reveal a statistically significant improvement in revenue performance following the 2007 tax reforms in Nigeria. The mean revenue during the pre-reform period was 77,050.21, while the post-reform period showed an increased mean revenue of 2,732.86, with a t-statistic of 3.40 and a p-value of 0.0052. This substantial difference suggests that the tax reforms introduced in 2007, which focused on granting administrative and financial autonomy to the Federal Inland Revenue Service (FIRS), automation, and restructuring, were effective in enhancing the overall revenue generation capacity of Nigeria’s tax administration system. This finding aligns with several studies that report a positive impact of tax reforms on revenue generation and efficiency. For instance, Ogbonna, & Ebimobonee (2022) found that tax reforms in Nigeria from 1986 to 2012 positively impacted economic growth, suggesting a clear connection between improved tax administration and economic performance. Likewise, Mertens (2003) and Akitoby (2018) highlighted the robust positive growth effect of tax reforms, indicating that well-implemented tax changes can bolster revenue and support broader economic objectives.

However, not all scholars agree on the benefits of tax reforms. Bahl and Bird (2008), Bird (2015), and Kete and Milionis (2019) present contrasting perspectives, arguing that the effects of tax reforms on revenue and growth can be mixed or even negative in some cases. They suggest that the success of tax reforms heavily depends on context, including administrative capacity, enforcement mechanisms, and economic conditions. In regions where these supportive conditions are lacking, reforms may yield minimal or even negative results.

CONCLUSION AND RECOMMENDATIONS

The statistically significant difference between pre-and post-reform revenue levels provides strong evidence that the 2007 reforms had a meaningful impact on the performance of FIRS in revenue collection. The reforms appear to have improved efficiency and tax compliance, making a case for the positive role of systematic tax administration reforms in enhancing fiscal sustainability the findings from this study provide strong evidence that the 2007 reforms positively impacted FIRS’s revenue collection performance in Nigeria. By granting FIRS autonomy, introducing process automation, and enhancing taxpayer education, the reforms addressed some critical structural issues within Nigeria’s tax system. The significant increase in revenue generation observed in the post-reform period demonstrates the effectiveness of these strategies in bolstering fiscal capacity and administrative efficiency. These results support the broader literature suggesting that targeted tax administration reforms can improve tax revenue and compliance when properly implemented. At the same time, the contrasting views in existing studies remind us that while tax reforms can be beneficial, their effectiveness depends on local factors and policy execution.

Based on the study findings, the following recommendation is proposed; Expanding digital and automated systems within tax administration can improve compliance and minimize revenue leakages. Enhanced data management and automated processing can reduce errors and increase collection efficiency. Increasing public understanding of tax obligations and the benefits of compliance is crucial for further improving revenue performance. A focused taxpayer education program could help mitigate resistance to compliance and encourage broader participation in the tax system.  FIRS should continue to evaluate and streamline its internal processes to eliminate inefficiencies, reduce bureaucratic delays, and maintain agility in adapting to policy or economic changes. Instituting periodic assessments of tax reforms will help FIRS identify successful strategies and areas for improvement. This approach will ensure that tax administration remains aligned with best practices and responsive to evolving economic and social needs.

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