How to calculate a tax refund
A refund is simply the gap between the tax actually deducted from you and the tax you legally owed for the year. Recompute the correct liability with every allowance, credit and expense applied, then compare it to what your payslips show you paid.
The rule
Refund = tax actually paid − tax correctly due after all allowances, credits and expenses
Do it automatically — Tax refund estimatorStep by step
- 1Total the tax and contributions deducted across all payslips for the year.
- 2Recalculate the correct liability using your full-year income.
- 3Apply anything you missed — work expenses, pension relief, medical or tuition credits, marriage allowance.
- 4The difference is your estimated refund; claim it through the tax authority, not your employer.
What trips people up
- • Mid-year job changes and emergency tax codes are the most common cause of overpayment.
- • Claims are usually limited to the last four tax years, so old refunds expire.
Common questions
How long does a refund take?
Typically a few weeks online, longer if the claim needs manual review or evidence.
Do I need receipts?
For expense-based claims yes — keep them for several years in case of review.
Skip the maths
Very rough estimate of a possible refund from overpaid tax or missed allowances.
Open the could you be owed money? tool