The seafarers tax deduction most searchers are asking about is the UK’s Seafarers’ Earnings Deduction (SED), which lets qualifying UK-resident mariners deduct 100% of their seafaring earnings from income tax and can wipe that tax bill down to zero. American merchant mariners have no direct equivalent, but they may be able to exclude up to $132,900 of foreign earnings in the 2026 tax year under the Foreign Earned Income Exclusion, subject to a physical presence test that treats international waters as a dead zone. The rules in both countries are strict on paperwork and day-counting, and small mistakes are expensive.
What the UK Seafarers’ Earnings Deduction Removes
Under section 379 of the Income Tax (Earnings and Pensions) Act 2003, the SED equals the full amount of qualifying earnings attributable to the eligible period. That means 100% of your seafaring pay for the qualifying stretch drops out of your taxable income. Leave pay you receive immediately after the eligible period ends also counts, provided it falls within the same tax year.1Legislation.gov.uk. Income Tax (Earnings and Pensions) Act 2003 – Section 379
One boundary to know up front: the SED only reduces income tax. National Insurance is calculated separately under different rules, so even a successful claim that eliminates your income tax will still leave NI owing on the same earnings.
Who Counts as a Qualifying Seafarer
You need to be an employee performing duties on a ship during a voyage. The law excludes fixed offshore installations that aren’t crewed by seafarers, along with platforms maintained for mineral exploration or extraction.2Legislation.gov.uk. Income Tax (Earnings and Pensions) Act 2003 – Section 378 A stationary rig bolted to the seabed is out. The vessel has to be capable of navigation.
Self-employed mariners can’t claim the SED; the relief is for PAYE employees. Crown employees, including Royal Navy sailors, are excluded, though Royal Fleet Auxiliary staff qualify if they meet the other conditions.3GOV.UK. Seafarers Earnings Deduction: Tax Relief if You Work on a Ship You must be resident in the UK or in another EEA state.
Your duties have to be performed wholly or partly outside the United Kingdom, and the voyage must include at least one call at a foreign port during the relevant tax year. A ship that only shuttles between domestic ports won’t support a claim.4HM Revenue & Customs. Employment Income Manual – Seafarers Earnings Deduction: General Conditions If you hold more than one seafaring job in the same tax year, each employment has to satisfy the foreign port requirement on its own.
The 365-Day Eligible Period
The core timing test is an eligible period of at least 365 days made up mainly of days when you were absent from the UK. You don’t need to be at sea the entire time. Non-work days spent outside the UK still count, including shore leave in foreign ports and holidays abroad.5HM Revenue & Customs. HS205 Seafarers Earnings Deduction
Whether a given day counts as absent turns on where you are at midnight. Outside the UK at midnight, absent. Inside, not. The rule is mechanical, so tracking your location day by day matters.
Return visits to the UK during the eligible period are allowed, but two limits apply:
- No single visit can exceed 183 consecutive days. One longer stay breaks the eligible period outright.
- Your cumulative UK days can’t exceed half the total days from your first day abroad to the last day of your overseas period after that return visit.
Breach either limit and the eligible period is lost. You start building a new 365-day stretch from scratch. This is where most claims come apart. Seafarers who take extended home leave without counting the ratio often find out too late that they’ve blown it. A simple log of your midnight location, updated after each trip home, is the difference between a clean claim and an expensive surprise.5HM Revenue & Customs. HS205 Seafarers Earnings Deduction
Getting an NT Tax Code So You Stop Overpaying
Rather than paying income tax all year and reclaiming it later, you can ask HMRC to issue an NT (No Tax) code so your employer stops withholding altogether. The money stays with you instead of sitting with HMRC until the refund comes through.
To qualify for the NT code, you must be a UK resident in PAYE employment on a vessel accepted as a ship for SED purposes, file a Self Assessment return each year, and either hold a contract of at least 12 months or have worked continuously for the same employer for at least 6 months outside the UK.
HMRC won’t issue the NT code until it has processed your first successful SED claim. That first claim can be made 12 months from the start of your seafaring employment or from the start of the previous tax year, whichever is later. You apply using form R44.3GOV.UK. Seafarers Earnings Deduction: Tax Relief if You Work on a Ship
If your circumstances change and you stop qualifying, tell HMRC straight away. If it turns out you weren’t entitled to the code, you’ll be asked to repay all the underpaid tax in one lump sum.3GOV.UK. Seafarers Earnings Deduction: Tax Relief if You Work on a Ship Only apply once you’re confident your sailing pattern will hold for the year.
Records HMRC Expects and How to File
SED claims go through Self Assessment. HMRC’s Help Sheet HS205 on GOV.UK walks through the eligible period calculation step by step, and the figures then transfer to the Additional Information pages of your tax return.5HM Revenue & Customs. HS205 Seafarers Earnings Deduction
HMRC may check your claim and expects you to hold on to supporting documents:
- Completed HS205 working sheet
- Seafarer’s discharge book showing when you joined and left each ship
- Air tickets and travel vouchers showing movements between ports and the UK
- Hotel bills and other receipts
- Passports and visas with entry and exit stamps
- Freeboard logs from the ships you served on
HMRC may also contact your employer directly to verify voyage and crew details.3GOV.UK. Seafarers Earnings Deduction: Tax Relief if You Work on a Ship Online filing is faster than paper. Refunds typically arrive within a few days to around eight weeks, depending on whether HMRC runs additional security checks.
US Mariners and the Foreign Earned Income Exclusion
American merchant mariners don’t have a direct SED equivalent, but they may qualify for the Foreign Earned Income Exclusion (FEIE) under Internal Revenue Code section 911. For the 2026 tax year the exclusion is up to $132,900 of foreign earned income.6Internal Revenue Service. Rev. Proc. 2025-32
To claim the FEIE you must meet the physical presence test: 330 full days present in a foreign country or countries during any 12-consecutive-month period. A full day means 24 hours from midnight to midnight, and the 330 days don’t have to run consecutively.7Internal Revenue Service. Foreign Earned Income Exclusion – Physical Presence Test
Here’s the catch that trips up mariners. Time spent on or over international waters does not count as time in a foreign country.7Internal Revenue Service. Foreign Earned Income Exclusion – Physical Presence Test Weeks of open ocean between ports contribute nothing to the 330-day count. Only days physically present in a foreign country at port or anchored in foreign territorial waters qualify. For deep-sea mariners who spend most of their time in international waters, hitting 330 qualifying days can be nearly impossible.
Your tax home also has to be in a foreign country, meaning your primary place of work sits outside the United States. If you regularly return to a US home between voyages, the IRS is likely to treat the US as your abode, which disqualifies you regardless of the day count. The claim is filed on Form 2555 attached to Form 1040.8Internal Revenue Service. About Form 2555, Foreign Earned Income
State Tax Protection for US Mariners
Federal law shields US merchant mariners from being taxed by every state whose waters they cross. Under 46 U.S.C. section 11108, a crewmember who performs regularly assigned duties on a vessel operating on navigable waters in two or more states can only be taxed by the state where they reside.9Office of the Law Revision Counsel. 46 USC 11108: Taxes Licensed pilots operating across state lines get the same protection.
The statute also bars states from withholding tax on wages earned by masters and seamen in foreign, coastwise, intercoastal, or interstate trade. The one exception is coastwise trade between ports in the same state, where withholding is allowed only if the seaman voluntarily agrees to it with the employer.9Office of the Law Revision Counsel. 46 USC 11108: Taxes If a state other than your home state is trying to tax your mariner income, this is the statute to point at.
US Business Expense Deductions
The Tax Cuts and Jobs Act suspended the deduction for unreimbursed employee business expenses from 2018 through 2025. That suspension is scheduled to expire, so W-2 maritime employees should be able to deduct qualifying unreimbursed expenses again starting with the 2026 tax year as miscellaneous itemized deductions on Schedule A. Whether Congress extends the suspension is unresolved, so check current law before filing.
Self-employed mariners weren’t affected by the suspension and continue to deduct ordinary and necessary business expenses on Schedule C. Common items include licensing and credentialing fees, required training courses, safety gear and work clothing not suitable for everyday wear, and tools or equipment you supply yourself.
Per Diem Rates for Transportation Workers
Mariners classified as transportation industry workers can use the IRS special per diem rate for meals instead of tracking every receipt. For the period beginning October 2025 the rate is $80 per day within the continental United States and $86 per day outside it.10Internal Revenue Service. 2025-2026 Special Per Diem Rates The incidental-expenses-only rate is $5 per day.
Training and Education Costs
Training expenses are deductible when they improve skills you already use in your current profession. A chief mate taking a course to upgrade an existing license qualifies. Someone who has never worked at sea paying for initial credentialing generally does not, because the IRS treats that as qualifying for a new trade rather than maintaining an existing one. The IRS has historically scrutinized mariner returns claiming education costs, so keep clear records showing the link between the training and the job you’re already doing.