If you claim the Seafarers' Earnings Deduction (SED), you already know how much of a pain it is tracking qualifying days. Spreadsheets, guesswork, hoping you haven't accidentally broken a qualifying period while ashore. And if you get it wrong, you lose the claim.

SeaClaim fixes that. Log your voyages, and it works out the rest - including telling you why you're eligible or not. Not just a green tick or a red cross. The actual reasoning: which rule, which dates, how far short.

See Where You Stand Right Now

Open the app and you'll see your days in hand before a rule break, your predicted fail date, and how close you are to 183 UK days. Check it before you book shore leave. Check it before you sign a contract. The numbers are there.

The Algorithm

Full HMRC HS205 methodology. Not a rough estimate - the actual working sheet logic, tested against hundreds of scenarios. Mid-period breaches, 183-day truncation, multi-year qualifying windows. It handles the awkward cases.

You can see the full breakdown for every qualifying period: which voyages counted, which tax years are claimable, and why. If something failed, it tells you the reason.

What You Get

- Voyage Logging: Pick your dates. That's it. SeaClaim does the rest.
- Live Dashboard: Status, voyage history, eligibility progress. One screen.
- Risk Metrics: Days in hand, fail date, 183-day UK tracking. Plan your time ashore around the numbers.
- Notifications: Warns you before you hit the half-day threshold or 183 consecutive UK days.
- HS205 Export: A completed HMRC working sheet PDF ready for your Self Assessment or your accountant.
- CSV Export: Voyage records and eligible periods as spreadsheets.

Merchant vessels, offshore support vessels, ferries, cruise ships, commercial shipping - if you're on a qualifying ship with foreign-port voyages and claiming SED tax relief, this is built for you.

SeaClaim is an independent app, not affiliated with HMRC or any UK government entity. The eligibility rules it implements are based on official HMRC guidance on the Seafarers' Earnings Deduction: https://www.gov.uk/guidance/seafarers-earnings-deduction-tax-relief-if-you-work-on-a-ship. This app does not provide tax advice. Verify figures before submitting to HMRC.