HMRC self-assessment tips for agents

Susan Cattell introduces some self-assessment tips for agents from HMRC.

HMRC has provided some useful SA tips for agents ahead of the 5 October notification deadline. 

The information is divided into three categories:

• Actions to take now
• New for 2024-25
• 2025/26 and beyond

If you have any comments, please let us know by emailing tax@icas.com – we will pass on any feedback to HMRC.

HMRC’s SA tips for agents

Actions to take now

Check if your client needs to do a tax return

Use HMRC’s online checker to see if your client needs to submit a tax return. It’s quick and easy to use and provides a tailored response on whether they need to complete a tax return. 

Notify by 5 October 2025

Clients with untaxed income, have a legal obligation to tell HMRC. For ease and speed, use the online forms on GOV.UK to register your client for self assessment. 

Reactivating accounts

If your client has previously been in self assessment and didn’t submit a tax return last year, make sure their account is reactivated before submitting their 2024-25 tax return. They do not need to register again, as they already have a Unique Taxpayer Reference.

To reactivate their account, use the CWF1 or SA1 online forms. 

Why registration and reactivation matters

Submitting a tax return without registering or reactivating an account can delay processing, lead to incorrect tax calculations, or trigger repayments that HMRC will need to recover.

Agent Authorisation

Make sure your clients completed the 64-8 online form and it includes the correct agent code so HMRC can link the customer to the agent. Using our online service is quicker, but if you can’t use it, you can complete a paper form and post it to HMRC. 

No longer need to submit a tax return? 

Tell HMRC as soon as possible. If a tax return isn’t submitted, then a penalty may be issued.

What’s new for the 2024-25 tax year

Cash Basis becomes default (from 6 April 2024)

Cash Basis is now the default for sole traders and partnerships. Instead of recording income and expenses when they are invoiced or billed (as in traditional accruals accounting), you record them only when money is received or paid. 

Key changes include: 

• No turnover limit to join
• £500 interest cap removed 
• No need to account for debtors, creditors, stock and work in progress 

More information: Cash basis: Overview - GOV.UK

Capital Gains Tax (CGT) updates (from April 2024)

• New rates for disposal apply on or after 30 October 2024 (excluding residential property, Business Asset Disposal Relief (BADR), Investors’ Relief or carried interest). The self assessment tax return won’t automatically apply the new rates, so the adjustment calculator must be used to calculate the correct CGT, and the figure added to the SA108, SA905 or SA970.
• The higher rate for residential property was reduced from 28% to 24% in April 2024. 
• The annual exempt amount was reduced to £3,000 for 2024-25.
• The SA108 now includes new boxes for BADR, Crypto gains and carried interest.
• From 30 October 2024 the Investors’ Relief Lifetime limit has been reduced from £10m to £1m to align with the Business Asset Disposal Relief lifetime limit.

For 2025-26 and beyond

There are several important updates and changes to tax rules and reporting 
requirements set to take effect in the coming years.

Making Tax Digital for Income Tax (from April 2026)

This is the biggest change to self assessment since its introduction. From April 2026, if your total turnover from self-employment and property is above £50,000, you’ll need to use recognised software to keep digital records of income and expenses, send HMRC quarterly updates, and submit your annual tax return. 

More information: Find out if and when you need to use Making Tax Digital for Income Tax. 

Tax residence regime (from April 2025)

Previous tax rules for non-domiciled status have ended and have been replaced with a system based on tax residence.

The main areas of the reforms include: 

• End of domicile based taxation: All long-term UK tax residents are now taxable on their worldwide income and gains and will need to report their worldwide income and gains, and make any claims for relief, through their self assessment tax return.
• 4-year Foreign Income and Gains (FIG) regime: New UK tax residents, who haven’t been UK tax resident in the past 10 years, can claim 100% relief on foreign income and gains through their self assessment tax return for their first four years of UK tax residency.
• Temporary Repatriation Facility (TRF): For a limited period of three tax years, individuals who previously claimed the remittance basis can remit foreign income and gains derived pre-6 April 2025 into the UK at a reduced tax rate. To make a designation under the TRF, an election must be made in a self assessment tax return for the relevant tax year.
• Overseas Workday Relief (OWR): This relief has been reformed by removing the need to keep the income offshore, extend the period that employees can benefit from the relief from 3 to 4 years and introduce an annual financial limit on the amount of relief that can be claimed through self assessment.

More information: Changes to the taxation of non-UK domiciled individuals - GOV.UK.

Furnished Holiday Lettings (FHL) abolished 

From 6 April 2025:

• Income from Furnished Holiday Lettings (FHL) will no longer be treated separately and will be combined with other property income for tax purposes.
• The changes apply to Corporation and Capital Gains Tax from 1 April 2025, and Income Tax from 6 April 2025.
• All property income, including Furnished Holidays Lettings (FHL), must be reported together in the 2025/2026 self assessment tax return, due by 31 January 2027. 

More information: Furnished holiday lettings tax regime abolition - GOV.UK 

Cryptoasset Reporting Framework (CARF) 

From January 2026, UK cryptoasset users must provide personal details to their cryptoasset service providers or face penalties of up to £300. The Cryptoasset Reporting Framework (CARF) will require cryptoasset service providers to collect and report personal and transaction data to HMRC. This is part of the UK’s wider effort to ensure everyone pays their fair share of tax. 

The penalty for not complying with the CARF is separate from any penalties due to the non-payment of tax on cryptoassets. 

More information: Information you'll need to give to UK cryptoasset service providers - GOV.UK

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