New digital process for NI refunds

It's now possible to claim a refund of overpaid Class 1 NI online, but only if HMRC writes to you about it first. HMRC systems use the data it holds to identify individuals that may have overpaid Class 1 NI. This could be due to an error made by your employer or because you had multiple jobs during a tax year.

However, like all HMRC systems, it isn't perfect and there's a chance the information it holds is wrong. If you receive a letter from HMRC about overpaid Class 1 NI, you first need to check whether the details are accurate. Errors can be corrected when you apply for a refund. If you think you may have overpaid NI, but haven't received a letter, you can use HMRC's  tool to find out how to claim it. Spoiler: if your employer can't help you need to write to HMRC.