When you pay your Corporation Tax to HMRC, you must use the correct payment reference number. Without it, HMRC cannot match your payment to your company’s tax account. This can cause delays, misallocated payments, and potentially trigger penalties, even if you paid on time.
This guide explains what the reference number looks like, where to find it, and how to work it out if you do not have it to hand.
What Does the Reference Number Look Like?
Your Corporation Tax payment reference number is 17 characters long. It looks like this:
1234567890A00102A
Here is what each part means:
•First 10 digits (e.g. 1234567890) — your Corporation Tax Unique Taxpayer Reference (UTR)
•Next 4 characters (A001) — a fixed code, the same for every company
•Next 2 digits (e.g. 02) — the accounting period you are paying for (01 = first year, 02 = second year, and so on)
•Final character (A) — a fixed letter, the same for every company
Where Do You Find Your Reference Number?
The easiest way is to check your HMRC Corporation Tax notice. HMRC sends this letter to your registered office address when your return is due. The payment slip inside includes your full reference number.
You can also find it in your HMRC online business tax account.
How to Work Out Your Reference Number
If you do not have your notice to hand, you can build the reference yourself using your UTR.
Step 1:
Find your 10-digit Corporation Tax UTR. You can find this on any HMRC letter or in your online tax account.
Step 2:
Add the fixed characters A001 immediately after your UTR.
Step 3:
Add the 2-digit code for the accounting period you are paying for. Your first accounting period is 01, your second is 02, and so on.
Step 4:
Add the final fixed letter A.
Example: If your UTR is 1234567890 and you are paying for your second accounting period, your reference number is:
1234567890A00102A
Why Does the Accounting Period Number Matter?
HMRC uses the accounting period digits to apply your payment to the correct tax year. If you use the wrong period number, your payment may go to the wrong year, leaving one year overpaid and another with an outstanding balance.
If you are unsure which accounting period number to use, check with your accountant before making the payment.
This guide is for information purposes only and was last updated in May 2026. If you are unsure about your Corporation Tax payment reference, speak to a qualified accountant or contact HMRC directly.