As the P11D completion deadline approaches, so does that for the P11D(b) for Class 1A National Insurance Contributions (NICs). Importantly, the payment deadline is later and must be accompanied by a reference number.
We are approaching the online P11D deadline for tax year 2025/26:
1. P11D to HMRC – by Monday 06 July 2026
2. P11D to employees – by Monday 06 July 2026
If a P11D has been completed, there may be an obligation to complete the P11D(b) and pay Class 1A NICs, so there are two other deadline dates to consider:
The Filing Date
The Social Security (Contributions) Regulations 2001 state the P11D(b) must be submitted by 06 July 2026. This is also confirmed at section 25 of HMRC's CWG5 Booklet ‘Class 1A National Insurance Contributions on Benefits in Kind’. However, this also says:
If we do not receive the return by 19 July it will attract a penalty of £100 per month or part month of lateness, for every 50 or part-batch of 50 employees provided with benefits.’
So, the deadline is 06 July, however, the penalty regime does not kick in until the 19th.
The Payment Date
Regulation 71 of The Social Security (Contributions) Regulations 2001 is interpreted in the CWG5 that gives us the date on which Class 1A NICs must be paid to HMRC:
- Sunday 19 July 2026 if paying by post; or
- Wednesday 22 July 2026 if paying electronically
For Bookkeepers
ICB recommends viewing the Gov.UK guidance on paying Class 1A. Whilst there is a late filing ‘grace period’ for P11D(b) filing, this does not apply for late payment. Importantly, the payment must be accompanied by the payment reference number which ensures HMRC allocate this as a payment of Class 1A rather than a regular PAYE payment.
The number is a 17-character mutation as follows:
- 13-character usual Accounts Office reference number; plus
- 2 characters indicating the calendar year in which the tax year finished, i.e. 26 for 2025/26 tax year; plus
- 2 characters indicating this is the thirteenth monthly payment, i.e. 13
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Tax year
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4 Digits
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2025/26
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2613
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