Nigeria’s 2026 Tax Transition: Old Tax Law or New Tax Acts — Which Applies to Your Business?

Say your company's accounting year ended on 31 December 2025. Your Companies Income Tax return for that year falls due sometime in 2026. A simple question: which law governs your liability — the law that was in force when you earned the income, or the law that's in force when you file the return?

As things stand, different arms of Nigeria's government have not settled on one answer. The tax authority has taken one position. The Minister of Finance's own transition guidelines take another. And the digital portal you are required to file through only lets you pick one of them.

How Two Arms of Government Ended Up Disagreeing

On 26 June 2025, President Bola Tinubu signed four landmark Acts into law in one sitting — the Nigeria Tax Act (NTA), the Nigeria Tax Administration Act (NTAA), the Nigeria Revenue Service (Establishment) Act, and the Joint Revenue Board (Establishment) Act — collectively the biggest rewrite of Nigeria's tax architecture since independence. All four commenced on 1 January 2026, replacing the Companies Income Tax Act and much of the machinery Nigerian businesses had filed under for decades.

In February 2026, the NRS issued internal guidance built around what amounts to a filing-based approach: if a company's Companies Income Tax return fell due in 2026, it would be assessed under the new Acts — regardless of when the accounting year the return actually covered had ended.

On 18 June 2026, the Minister of Finance issued the General Transition Guidelines for the Tax Acts 2025 — and took the opposite position. Under the Guidelines, tax treatment follows the basis period, not the filing date: income earned in an accounting period ending before 1 January 2026 remains taxable under the old, repealed law, no matter when the return is actually filed. A company with a 31 December 2025 year-end stays under the old Companies Income Tax Act, even filing in the second half of 2026.

That should have settled the question. It didn't. The Foundation for Investigative Journalism (FIJ), a Nigerian investigative outlet, has since reported on correspondence the NRS sent to tax practitioners after the Guidelines were issued, maintaining that the applicable law is fixed by the year a return is filed, not the year the income was earned, and that the Service has no authority to process 2026 filings under repealed legislation. Rev360, the NRS's new filing platform, had already been configured months earlier to enforce exactly that position — built before the Minister's Guidelines existed at all.

None of this left taxpayers with a choice to make. Before Rev360 even launched, the NRS's February 2026 directive already applied the filing-based approach through the outgoing TaxPro Max platform for returns falling due in 2026. When Rev360 went live at the end of April 2026, it inherited and hard-coded the same position. At any point since 1 January 2026, there has been exactly one route available for filing a 2026-due Companies Income Tax return, and it has enforced exactly one answer. No company selected which law would govern its return, any more than a driver selects which way a one-way street runs.

Not Just Old Law vs New Law — Two Different Questions

There is a more precise way to frame this, and it matters. The dispute is not simply whether the old law or the new law governs a 2025 accounting period. There are really two questions tangled together: which substantive law fixes the tax liability itself — what is actually owed — and which administrative and procedural framework governs how that liability is filed, paid, objected to, and enforced once 2026 arrives. A transition rarely flips every switch on the same day; procedure and substance can legitimately move at different speeds, and a defensible administrative position could exist somewhere in that distinction.

But that is not the argument the NRS has actually been making. Its correspondence to practitioners, as reported, does not claim procedure has simply changed. It claims the Service has no authority to process 2026 returns under repealed legislation at all — a position on substance, not process, and one that contradicts the Minister's Guidelines directly rather than sitting alongside them.

Enter the Organised Private Sector

By late June, the Organised Private Sector of Nigeria — a coalition representing more than 40 employers' associations, chambers of commerce, and business groups — had had enough. In an open letter, OPSN accused the NRS of implementing the reforms in a manner that contradicts the government's own transition framework, and called for direct presidential intervention, describing the situation as a deepening tax administration crisis.

Notably, OPSN was careful to frame this as a defence of the reform programme, not an attack on it. The group said its members remain willing, ready taxpayers who fully support the reform agenda — what they are asking for is one law to comply with, not two.

Why This Isn't a Technicality

This goes to one of the oldest principles in tax law: a tax obligation is generally fixed by the law in force during the period the income was earned, not by whichever law happens to be running the day you file. Retrospective taxation — being taxed under a law that did not yet exist when the income arose — is something courts have historically resisted, and preventing exactly that appears to be the point of the Minister's Transition Guidelines. If a filing platform overrides that principle by refusing to process returns any other way, businesses filing this year are effectively being pushed into a position the government's own guidance says should not apply to them.

The two regimes do not just differ by name. Thresholds, reliefs, levies and exemptions differ enough between the repealed law and the Tax Acts 2025 that which one applies can genuinely change what a company owes — this is not a paperwork dispute with no financial consequence attached to it.

A tax portal is a piece of administrative machinery. It is not a court, and it is not the law. Successful submission through Rev360 — or through TaxPro Max before it — was never a matter of taxpayer election; it reflects whichever position the platform enforced at the moment of filing, not a conclusion the taxpayer reached on the merits. That acceptance is evidence a form went through — nothing more. It is not evidence that the underlying tax treatment is correct, and businesses now carry risk they never had the opportunity to avoid.

What Businesses Caught in the Middle Should Do Now

For the calendar year-end scenario used throughout this piece, this is no longer a hypothetical about a future deadline. Companies Income Tax returns for a 31 December 2025 accounting year were due within six months of that year-end — by 30 June 2026. That deadline has already passed. Most companies with a December year-end that filed this year did so through Rev360, in whatever form Rev360 was configured to accept, whether or not that matches the position the Minister's Guidelines say should actually govern them. For those companies, the question is no longer “which law do I file under.” It is what to do about a return that may already have been filed under the wrong one.

If your CIT return is already filed (December 2025 year-end):

Establish which regime the platform assessed the return under at the time you filed — not a position anyone chose, but the only one the system permitted — and compare it against what the Minister's Transition Guidelines say should actually apply to your basis period.

Where there's a material gap between the two, treat it as an open question, not a closed one — successful submission is not the same as a settled tax position, and an objection or amendment may be worth pursuing.

Pull together the workings, correspondence, and portal constraints that shaped what was actually filed, and keep them on file now, while the details are still fresh — not after a query arrives.

If your CIT return is still due (non-December year-ends, or any other outstanding filing):

Compute the liability under both the repealed law and the Tax Acts 2025, and keep the workings on file — even where the portal will only accept one outcome.

Document, in writing and before submission, your own computed position under what you believe is the correct law — separately from whatever position the platform ultimately forces the filing into.

Where the platform genuinely allows no alternative to a position you believe is wrong, document that constraint itself — it may matter if the position is challenged later.

Either way:

Do not treat the platform's behaviour as the final word. The Minister's Transition Guidelines expressly prescribe the transition treatment applicable to pre-2026 accounting periods, and should therefore form an important part of the technical basis for assessing the appropriate filing position, irrespective of Rev360's current configuration.

Watch for the penalty-free grace period tax practitioners have publicly been calling for, and keep records that would support a later objection or amendment if the platform is eventually reconciled to the Guidelines.

Consider the financial reporting implications. Where the alternative interpretations produce materially different liabilities, that difference may need to be reflected as a current tax provision, an uncertain tax position, or a disclosure in the year's financial statements — not quietly resolved on a tax return and forgotten.

Numbers That Clear the Portal Aren't Necessarily Settled

A Companies Income Tax return that clears Rev360 is not the same thing as a return that reflects the correct law. Different arms of the same government have taken different positions on which law applies to your 2025 profits — and until that gap closes, it is not the NRS, and it is not the Minister, who will be answering for it. It is you.

This article analyses a live regulatory dispute and is intended for general professional and educational purposes. It does not constitute tax or legal advice for any specific company. The appropriate position will depend on the taxpayer's particular facts and the applicable law.

Joe Adinma, FCA, FCTI

Managing Partner

Joe Adinma & Co. (Chartered Accountants)

Sources

Organised private sector faults tax laws' implementation, Daily Trust (25 June 2026) — https://dailytrust.com/organised-private-sector-faults-tax-laws-implementation/

6 Months Into New Tax Regime, Federal Agencies Still Argue Over Which Tax Law Companies Should Obey, FIJ (25 June 2026) — https://fij.ng/article/exclusive-6-months-into-new-tax-regime-federal-mdas-still-argue-over-which-tax-law-companies-should-obey/

General Transition Guidelines for the Tax Acts 2025, issued by the Minister of Finance and Coordinating Minister of the Economy (18 June 2026), paragraph 10.1.2(1)

Tax Acts 2025 Transition Guidelines: Key Commercial Insights For Businesses, Mondaq (1 July 2026) — https://www.mondaq.com/nigeria/tax-authorities/1809940/tax-acts-2025-transition-guidelines-key-commercial-insights-for-businesses

Nigeria's tax transition and the rule of law, BusinessDay NG — https://businessday.ng/opinion/article/nigerias-tax-transition-and-the-rule-of-law-why-legal-certainty-must-remain-at-the-heart-of-tax-reform/

President Tinubu Signs 2025 Tax Reform Acts into Law (26 June 2025) — Andersen Nigeria, PwC Nigeria, EY Global tax alerts