Self Assessment Tax Refund: How to Claim, Check and Chase an HMRC Refund

What is a Self Assessment tax refund?

A Self Assessment tax refund is a repayment of tax that you have overpaid through the Self Assessment system.

For example, imagine you have already paid £4,500 towards your tax liability. Your completed tax return then shows that only £3,800 was ultimately due.

Subject to any other amounts HMRC can use the credit against, the £700 difference may be available as a tax refund.

A refund does not necessarily mean there was an HMRC error. Your final tax liability can change for several legitimate reasons.

HMRC confirms that taxpayers who have paid too much tax may be entitled to a repayment.

Why might HMRC owe you a Self Assessment tax refund?

There are several common reasons for overpaid Self Assessment tax.

It is worth understanding one important point about business expenses.

An allowable expense does not normally generate an equivalent cash refund. Instead, it reduces taxable business profit.

For example, a £1,000 allowable expense does not mean HMRC will automatically send you £1,000. The actual tax effect depends on your overall tax position.

Real Key Accountancy’s guide to allowable business expenses for sole traders explains how business expenses affect taxable profit.

How can you check if you are due a Self Assessment tax refund?

Start by checking your completed tax return and Self Assessment account.

Review:

• your final tax calculation;
• payments on account already made;
• other payments made to HMRC;
• PAYE tax deducted from employment income;
• CIS deductions, where applicable;
• income reported on the tax return;
• allowable expenses and tax reliefs; and
• any previous repayments or adjustments.

You can sign in to your Self Assessment account to see whether HMRC shows an amount available for repayment.

However, a credit balance does not always mean the entire amount will be paid into your bank account.

HMRC may allocate part or all of the credit against another amount becoming due.

How to claim a Self Assessment tax refund

If HMRC has processed your tax return and your account shows a repayable credit, claiming a refund can be straightforward.

1. Check your tax return first

Before requesting the money, make sure the tax calculation makes sense.

Pay particular attention if the refund is much larger than expected.

Check income, allowable expenses, tax deducted and payments on account against your records.

2. Sign in to your HMRC Self Assessment account

HMRC’s online services allow you to view your Self Assessment position.

If a repayment is available, you may see the option to “Request a repayment”. LITRG also confirms that taxpayers filing online can use this option when a repayment needs to be prompted.

3. Provide the required repayment information

Follow HMRC’s instructions and make sure any bank details or other repayment information are correct.

Depending on the circumstances, HMRC may pay a refund into a bank account, send a cheque or return funds to a card previously used to pay HMRC.

4. Check the repayment status

Your online account may show the repayment as pending while HMRC processes it.

Avoid submitting multiple repayment requests simply because the first one has not yet completed.

For official instructions, use HMRC’s Self Assessment tax refund guidance.

How long does a Self Assessment tax refund take?

There is no single guaranteed Self Assessment tax refund timescale that applies to every taxpayer.

Online returns will generally be dealt with sooner than paper returns. However, repayment timing can depend on:

• whether HMRC has processed the return;
• whether a repayment request is required;
• whether HMRC needs additional information;
• security and fraud-prevention checks;
• other outstanding HMRC liabilities; and
• how the refund is being paid.

Therefore, be cautious of websites promising that every HMRC Self Assessment refund will arrive within a fixed number of days.

HMRC provides a current service that allows taxpayers to check when they can expect a reply from HMRC. Its Self Assessment guidance directs taxpayers who have already claimed a refund to this service.

Filing your tax return early can also help you identify an overpayment sooner.

For the 2025/26 tax year, the normal online Self Assessment filing deadline is 31 January 2027. You do not need to wait until January 2027 to file if your return is ready.

See Real Key Accountancy’s Self Assessment deadlines guide for 2026/27 for the key filing and payment dates.

Why is my Self Assessment tax refund pending?

A pending Self Assessment refund means the repayment has been created but still needs to be approved and paid.

It does not automatically mean your refund has been rejected.

HMRC may carry out additional checks before releasing a repayment. These can form part of its processes for preventing incorrect or fraudulent refund claims.

HMRC may need to verify information such as:

• your identity;
• details on the tax return;
• the amount being reclaimed;
• tax already deducted;
• CIS deductions;
• repayment instructions; or
• information held elsewhere in its systems.

A repayment security check is also not necessarily the same as HMRC opening a formal enquiry into your tax return.

Can HMRC text you about a Self Assessment refund?

Yes.

HMRC states that it may send a text after you request a Self Assessment tax refund. A genuine HMRC text about this process may confirm that your refund is being processed and indicate when you can expect it.

However, HMRC states that these particular messages will not ask for personal or financial information or contain links to websites.

That distinction is useful if you receive an unexpected tax-refund text.

Can HMRC use your refund against payments on account?

Yes.

One of the most important Self Assessment refund rules involves payments on account.

Payments on account are advance payments towards a future Self Assessment tax bill. They are normally due in two instalments, on 31 January and 31 July, where the payments-on-account rules apply.

HMRC states that you may not receive a refund if Self Assessment tax is due within the next 45 days. Instead, the credit can be deducted from the amount you owe.

Example: refund used against your next tax payment

David submits his tax return and his Self Assessment account shows a £1,200 credit.

However, he also has a payment on account becoming due shortly.

HMRC may use some or all of the £1,200 against that upcoming liability rather than sending the full amount to David’s bank account.

Therefore, check your upcoming Self Assessment payments before assuming a credit balance will become cash in your bank.

Can you get a refund if your payments on account were too high?

Yes, potentially.

Payments on account are generally based on your previous tax position. Your actual circumstances can change.

For example, your:

• self-employed profits may fall;
• business may stop trading;
• taxable income may reduce; or
• tax deducted elsewhere may increase.

If you reasonably expect your tax liability to be lower, HMRC allows you to apply to reduce payments on account.

However, do not reduce them without a reasonable basis. HMRC states that interest may be charged if you reduce your payments too far and the eventual tax bill is higher than expected.

Where excess payments have already created a credit, a repayment may be available once HMRC has processed the relevant information.

CIS Self Assessment tax refunds for subcontractors

A CIS tax refund is one of the most common types of Self Assessment repayment for construction subcontractors.

Under the Construction Industry Scheme, contractors can deduct tax before paying registered subcontractors.

For a self-employed sole trader, these CIS deductions are payments towards the subcontractor’s eventual tax liability. They are not necessarily the final amount of tax owed.

Example: CIS deductions create a tax refund

Mark is a self-employed subcontractor.

During the year, contractors deduct CIS tax from his payments. After Mark reports his income, allowable expenses and CIS deductions through Self Assessment, his final tax liability is lower than the deductions already suffered.

The excess may become repayable.

This does not mean every CIS subcontractor is automatically entitled to a refund. The result depends on the individual’s complete tax position.

Keep all contractor deduction statements and check that the amounts entered on the return agree with your records. Missing or incorrect CIS information can affect the repayment calculation.

HMRC provides specific guidance for subcontractors claiming back CIS deductions.

What if your Self Assessment refund looks too high?

An unexpectedly large HMRC tax refund deserves a second look.

Before spending the money, check whether:

• employment income has been omitted;
• PAYE tax deducted has been entered incorrectly;
• CIS deductions have been duplicated;
• expenses have been entered twice;
• income has been missed;
• payments on account have been misunderstood; or
• another adjustment has been entered incorrectly.

The aim is not to produce the biggest possible tax rebate.

The aim is to calculate the correct Self Assessment liability and reclaim only money genuinely overpaid.

Good bookkeeping makes that easier because income, expenses and tax deductions can be checked against reliable records.

Real Key Accountancy provides accountancy and Self Assessment support for sole traders, self-employed professionals and small businesses.

Can you amend a Self Assessment return to claim a tax refund?

Yes.

If you discover an error that caused you to pay too much tax, you may be able to amend your Self Assessment return.

For example, you might discover:

• allowable expenses that were omitted;
• an incorrect income figure;
• incorrectly reported tax deductions; or
• another mistake affecting the tax calculation.

HMRC normally allows a Self Assessment return to be amended within 12 months of the statutory filing deadline.

After HMRC processes the corrected return, the revised calculation may produce a tax refund.

You may then need to request the resulting repayment through your online account.

How far back can you claim a Self Assessment tax refund?

If it is too late to amend the original return, you may still be able to make an overpayment relief claim.

Overpayment relief allows taxpayers to reclaim certain tax that should not have been paid where the normal amendment deadline has passed.

The usual deadline is four years after the end of the relevant tax year. Specific conditions and exclusions apply.

For example, LITRG explains that an overpayment relief claim relating to 2023/24 would generally need to reach HMRC by 5 April 2028.

Older tax refunds can become more complicated. Keep copies of calculations, returns, correspondence and evidence supporting the amount you believe was overpaid.

Common Self Assessment tax refund mistakes

A refund can be delayed or calculated incorrectly if the information behind it is wrong.

Common mistakes include:

Entering CIS deductions incorrectly. Check contractor deduction statements against the amount reported.

Confusing business expenses with a cash refund. Expenses reduce taxable profit rather than normally being refunded pound-for-pound.

Requesting repayment without checking the return. Investigate unexpected figures before relying on them.

Ignoring payments on account. HMRC may use your credit against tax becoming due.

Reducing payments on account too far. Interest can arise if the reduction proves excessive.

Repeatedly requesting a pending repayment. A further request will not necessarily speed up security checks.

Failing to correct an inaccurate return. If the tax calculation is wrong, address the underlying return rather than focusing only on the refund.

When might professional help with a tax refund be useful?

Many straightforward Self Assessment refunds can be handled directly with HMRC.

However, professional support may be useful if:

• your CIS deductions do not agree with your records;
• the refund is unexpectedly large or small;
• you have several sources of taxable income;
• you need to amend an earlier return;
• your bookkeeping is incomplete;
• you are unsure which expenses are allowable;
• payments on account are causing confusion; or
• HMRC has asked for information you do not understand.

Real Key Accountancy can help organise the bookkeeping and tax information behind a Self Assessment return.

If you need support checking your figures or preparing an accurate return, you can speak to Real Key Accountancy about the next practical step.