Recording a client's Tax ID and CAC number
How a firm collects, checks and records a Nigerian client's Tax ID and CAC number at onboarding, and what Achekam checks and leaves to the firm.
By Achekam · · 4 min read · For Accountants & audit firms in Nigeria
Two numbers sit at the top of every Nigerian business client's file: its registration number with the Corporate Affairs Commission and its Tax ID. Get either wrong and the error travels into every return, payment and letter the firm prepares. Get them right at onboarding and nobody has to think about them again.
Nigeria's move to a single Tax ID has made this both simpler and easier to get wrong. The Tax ID is now linked to the CAC number for businesses, so the two must agree with each other as well as with the client's records. This article sets out how to obtain and check both, and what Achekam does and does not do with them.
The Tax ID and its link to the CAC number
The FCT Internal Revenue Service's notice of 29 December 2025 describes the Tax ID as a unique, system-generated number assigned to all taxable persons in Nigeria. It is linked to the National Identification Number for individuals and to the CAC registration number for businesses and organisations.
The NRS says the same from its side: a Tax ID is obtained or retrieved on the National Tax ID portal using the person's foundational identity, which is the NIN for individuals and the CAC number for non-individuals. Its page on retrieving a Tax ID explains the process; note that the page's portal link still pointed to a firs.gov.ng address when it was checked.
For a business client, then, the CAC number comes first. A Tax ID retrieved with the wrong CAC number is the wrong Tax ID.
Retrieving and validating it
The FCT-IRS notice gives the steps for a registered entity: on the portal, choose the Corporate tab, select the organisation type and enter the CAC registration number, after which a 13-digit Tax ID is displayed.
Retrieval is not validation. The NRS says validating a Tax ID means checking that the number exists in the official records and matches the right personal or business details, which helps prove eligibility to employers, banks or government agencies. So the check that matters is a match: the business name shown against the Tax ID is the client's name as registered with the CAC.
The NRS also explains why accuracy matters. It says a Tax ID must be quoted accurately on all tax forms, payments and correspondence with tax authorities, and that a valid Tax ID makes a person eligible for services such as tax clearance certificates.
What Achekam checks, and what it leaves to the firm
Achekam's check is deliberately narrow. It checks only that a Nigeria Tax ID has 13 digits; it cannot confirm the number with the authority, because no public Tax ID verification API was found. The user retrieves the Tax ID on the portal and records the evidence. CAC numbers are normalised to digits and never length-checked, and a NIN is not accepted as a Tax ID.
That makes the evidence step essential. A 13-digit number that passes Achekam's check may still belong to another business. The firm's evidence, a dated capture of the portal result showing the client's name, is what shows the number is right.
The Jurisdiction section and the onboarding checklist
Each client's profile in Achekam has a Jurisdiction section with the client's own country and identifiers, which is where the CAC number and Tax ID belong. Each Nigerian engagement then shows its governing basis of regulator, standards, framework, company law and tax authority. A jurisdiction override is decided by a different person. The wider pack set-up is in setting up the Nigeria or Kenya pack.
The Onboarding page shows a readiness checklist for each new client, built from what the server holds, and offers "Mark active" only when every item is met. The items are registration and income tax numbers, an active service, a contact, an engagement and an account manager. A client without a recorded Tax ID therefore cannot be marked active, which keeps an incomplete record from slipping into the firm's working list.
Evidence to keep
| Item | Source | Evidence on file |
|---|---|---|
| CAC registration number | The client's CAC certificate or status report | Copy of the certificate |
| Tax ID | Retrieved on the National Tax ID portal with the CAC number | Dated capture showing name and Tax ID |
| Name match | Portal result against CAC records | Note by the person who checked |
| Recorded in Achekam | Jurisdiction section | Identifiers entered; checklist item met |
Keep the capture even after the client is active. When a tax authority, a bank or the client's own customers question the number later, the firm can show where it came from and when it was checked.
Onboarding questions for a new client
Put these to every new Nigerian business client, ideally in the first information request:
- What is your CAC registration number, and may we have a copy of the certificate?
- Have you retrieved your Tax ID on the National Tax ID portal? If so, please send the result.
- Is the name on the Tax ID result exactly the name on your CAC certificate?
- Have you used any older tax identification numbers that may still appear on your records or customers' records?
- Who at your business may we contact about tax correspondence?
If the client has not yet retrieved its Tax ID, the firm can do it with the CAC number and keep the evidence itself. For the Kenyan equivalent, and how the two systems compare, see the Nigerian Tax ID and the KRA PIN.
General guidance only, not advice on your own circumstances. Tax and payroll rules change: check the current position with the authority or your adviser.
