The SA303 applies to reduce your Payments on Account when you expect this year's tax to be lower than last's. Risky if you under-claim — HMRC will charge interest on the shortfall.
Related terms
Stop dreading tax. Start ignoring it.
Get a fixed-fee quote in 60 seconds. No signup, no card, no sales call. We'll just tell you what it'll cost and how fast we can file it.