UK Self-Assessment Taxpayers Overpaid? How to Check and Reclaim Your Money

If you’ve just filed your Self-Assessment tax return and paid your bill with a sigh of relief, you might assume your tax affairs are settled. But what if we told you there’s a possibility you’ve paid too much?

It’s a surprisingly common situation. Whether due to a simple error, a missed expense, or a change in your circumstances, thousands of UK taxpayers overpay HMRC each year. With the January deadline now behind us, this is the perfect moment to ensure you’ve paid exactly what you owe and not a penny more.

If you suspect a mistake or have ever wondered, "Could I be due a tax rebate UK?", this guide will walk you through how to check for an HMRC tax overpayment and exactly how to reclaim your money.

Why Do Self-Assessment Overpayments Happen?

Understanding the common causes is the first step to identifying if you might be affected. Overpayments aren't always about dramatic errors; they're often due to overlooked details.

1. Common Mistakes on the Tax Return (SA100)

• Incorrect Figures: Transposing numbers, mis-typing income amounts, or entering the same data twice.

• Forgotten Expenses: Omitting allowable business expenses, professional subscriptions, charitable donations under Gift Aid, or flat-rate deductions for working from home.

• Misunderstood Allowances: Not claiming Marriage Allowance or Blind Person’s Allowance when eligible.

• Wrong Tax Code Carry-Over: If you were on an emergency tax code for part of the year and didn't update your return accordingly.

2. Changes in Your Circumstances

• Leaving a Job: If you left employment part-way through the tax year and had significant untaxed personal allowance remaining, but your self-assessment didn't fully account for it.

• Multiple Incomes: Having several income streams (e.g., employment, self-employment, rental income) can complicate calculations, increasing the chance of overpayment.

• Pension Contributions: Making a large personal pension contribution after you've filed, or forgetting to include contributions that qualify for higher-rate tax relief.

3. HMRC System Errors

While less common, delays in processing information from employers or pension providers can sometimes lead to HMRC using outdated data to calculate what you owe.

Step-by-Step: How to Check for a UK Self-Assessment Refund

You don’t need to be certain you’ve overpaid to check. A proactive review is just good financial hygiene.

Step 1: Log into Your HMRC Online Account

This is your central hub. Go to the Government Gateway and access your ‘Self-Assessment’ account. Here, you can view your:

• Tax calculation: HMRC’s breakdown of how your liability was worked out.

• Payment history: A record of all payments on account and balancing payments.

• Statement of account: This shows your current position, whether you are ‘in credit’ (they owe you) or ‘in debit’ (you owe them).
  
  

Step 2: Review Your Tax Calculation for the Year in Question

Scrutinise the official calculation HMRC produced after you submitted your return. Check that:

• All your income sources are listed and correct.

• All your claimed allowances and reliefs are present.

• The personal allowance applied is correct for your income level.
  
  
  

Step 3: Cross-Reference with Your Records

Gather your own records: P60s, P11Ds, bank statements, expense receipts, and a copy of the tax return you submitted. Compare them line-by-line against HMRC’s calculation. Pay special attention to expenses you claimed, ensure they were all included.

Step 4: Understand Your "Statement of Account"

This is the crucial document. If the box says “You are due a repayment” or shows a credit balance, HMRC owes you money. Sometimes this can be because you've made Payments on Account that were higher than your final tax bill.

How to Claim Your Money Back from HMRC

If your review confirms an overpayment, here’s what to do:

1. If You’ve Just Filed (Within Last 3 Days):

HMRC’s systems will often identify an overpayment automatically and issue a refund. This usually takes 4-6 weeks.

2. If It’s Been Longer, or You Spotted an Error:

• Amend Your Return: You have up to 12 months after the 31st January filing deadline to amend your return online. This is the cleanest way to correct an error. Once you submit the amendment, HMRC will recalculate your liability and process any refund due.

• Contact HMRC Directly: If amending the return feels complex, you can call the Self-Assessment helpline. Explain you believe you’ve overpaid and what you think the error is. They can review it with you.

3. How You’ll Get Paid:

Refunds are typically made by direct transfer to the bank account HMRC holds on file for you. Ensure your account details are up to date in your online profile.

Important Things to Know About Tax Refunds

• Time Limits: For an in-year overpayment, the standard time to claim is four years from the end of the relevant tax year. Don’t delay.

• Beware of Scams: Be extremely wary of cold calls, emails, or texts claiming you are due a tax refund and asking for your bank details. HMRC will never contact you out of the blue about a refund in this way. Always initiate contact via your official Government Gateway account.

• Set-Off: HMRC may sometimes automatically use a credit to offset another tax debt you have (e.g., VAT or PAYE). They should notify you if they do this.

Your Quick-Reference Checklist

• Log into your HMRC online account.

• Check your ‘Statement of Account’ for a credit balance.

• Review your official tax calculation against your personal records.

• If an error is found, amend your return online or call HMRC.

• Ensure your bank details are up to date with HMRC.

• Stay vigilant for refund scams.

Check if HMRC Owes You Money

Completing your Self-Assessment is an achievement, but your financial diligence shouldn’t stop at submission. A proactive review could uncover an unexpected refund, putting money rightfully back in your pocket.

At Boobooks Accounting, we help our clients navigate every aspect of their tax affairs with clarity and confidence. From ensuring returns are accurate from the outset to reviewing historic positions for potential overpayments, we’re here to ensure you pay no more tax than the law requires.

Why let your money sit with HMRC if it belongs to you?

Check if HMRC owes you money.