SA liabilities may include income tax, class 4 national insurance contributions and capital gains tax. The deadline for paying tax due under SA for 2024/25 is 31 January 2026. 

HMRC will charge interest on any tax paid late. The rate of interest on underpaid tax is currently 8%. Any tax still outstanding after 30 days will attract a late payment penalty of 5%.  

Making a payment 

HMRC has published guidance explaining how to make a payment. In some cases, HMRC will automatically collect the SA tax due by making an adjustment to the taxpayer’s pay as you earn (PAYE) tax code (“coding-out”). The conditions for coding-out include that: 

• the taxpayer pays tax through PAYE; 
• their total SA tax bill for 2024/25 is less than £3,000; and
• they submitted their 2024/25 tax return by 30 December 2025 (31 October 2025 if a paper return was submitted).  

It is possible to opt out of coding-out and to pay the tax due outside of PAYE when completing the tax return.

Claiming a repayment 

The taxpayer may find that they are due a tax repayment on completing their tax return. In the past, taxpayers have experienced delays in receiving repayments from HMRC. The HMRC service dashboard currently states that HMRC will aim to process the refund within two weeks from the date it received the return. Refunds may take longer due to HMRC’s security measures, where the return is filed on paper or where a loss or relief is carried back.  

HMRC has published an online tool that taxpayers and agents can use to see when they can expect a reply from HMRC, including processing a tax refund on receipt of a tax return.  

Tips for agents 

HMRC has published the following tips for agents to ensure that repayments are processed quickly:  

• where the taxpayer is new or returning to SA, delay submitting the return until the taxpayer has received a notice to file a return;
• check the taxpayer’s details are correct and up to date, including their bank sort code and account number, unique taxpayer reference (UTR), national insurance number, name, and address (see the guidance on avoiding address rejections below);
• leave 14 days after making a payment before requesting a repayment;
• use the post-bankruptcy UTR for taxpayers who were previously bankrupt;
• notify HMRC of the capacitor if the taxpayer died before submitting their tax return and before requesting a repayment; and
• encourage the taxpayer to receive their repayment electronically (ie, by BACS).