Offshore Payroll Guide

Offshore payroll catches finance teams out for one reason. The default assumption is that someone working in Aberdeen and someone working 120 miles east on a North Sea platform are treated the same way for PAYE.

They are not, and the rules that apply to the second person are not the rules that apply to a merchant seafarer on a container ship either.

A misclassified rotation can turn a 40% SED relief claim into an HMRC enquiry. Getting an A1 certificate wrong on a Spain posting leaves your employer carrying Class 1 NIC in the UK and host-country contributions in Spain for the same month.

• We walk through Seafarers’ Earnings Deduction eligibility
• UKCS rules for rig and wind workers
• Appendix 5 modified payroll for UK staff abroad
• and the residence traps that flip a two-on two-off pattern into full UK PAYE

Which offshore workers qualify for the Seafarers’ Earnings Deduction?

SED is the most generous relief in UK payroll and the most tightly policed.

It gives you 100% income tax relief on earnings from employment as a seafarer, but the eligibility bar is narrow and HMRC checks claims against crew lists.

Three tests must all pass. First, the eligible period must be at least 365 days.

Second, at least half of that period must be spent outside the UK. Third, no return visit to the UK can exceed 183 consecutive days without breaking the period.

The rules sit in ITEPA 2003 s.378-385, and HMRC’s HS205 helpsheet is the practical reference.

The vessel matters as much as the voyage. A qualifying ship is one engaged in navigation, which rules out fixed or semi-fixed offshore installations. Oil and gas production platforms, FPSOs, jack-up rigs, and floating wind installations during operational phase are not ships for SED purposes.

A dive support vessel or a cable-laying ship usually is.

You still operate PAYE on every pay run for a seafarer. SED is claimed by the employee through self-assessment using form HS205, not coded into their tax code.

If you apply an NT code by mistake and the claim later fails, the PAYE arrears sit with the employer.

Rule: before you classify anyone as SED-eligible, pull a written confirmation from the vessel operator that the ship is engaged in navigation. A rig masquerading as a ship is the fastest way to lose a claim.

How does PAYE work on oil rigs, wind farms, and other UKCS installations?

Workers on installations inside the UK Continental Shelf designated area are in a specific tax regime that you need to know cold. FA 1973 s.38 treats earnings from activities on the UKCS as UK-source.

ITEPA 2003 s.41 pulls those earnings into PAYE even if the employer is offshore and the worker is not UK-resident.

This catches a lot of foreign labour-supply arrangements. A Norwegian contractor sending welders to a UKCS platform cannot, by default, keep payroll in Norway.

HMRC expects a UK PAYE scheme for those workers, or a certificate of no-tax-deduction (an NT authorisation) granted under the oil and gas bareboat chartering exemption.

Class 1 NIC follows the same logic inside the UKCS designated area for most cases. If the employer is outside the UK but the work is inside the designated waters, the UK-resident principal contractor is often the liable secondary contributor.

Check HMRC’s CA28 offshore manual and confirm in writing with the licence holder who is filing the FPS.

Wind farms now sit in the same regime. Since the Finance Act 2014 extension, renewable installations within the UKCS designated area are treated the same as oil and gas for PAYE purposes.

A crew on an offshore wind turbine jack-up is on UK PAYE from day one.

Scenario rule: if the installation sits inside the UKCS designated coordinates and is engaged in extraction or generation, you are running UK PAYE.

The nationality of the worker, the flag of the vessel, and the domicile of the employer do not change that answer.

What residence test applies to offshore workers on a rotation?

North Sea rotations typically run two-on, two-off or three-on, three-off. On paper that looks like half a year outside the UK.

In practice it almost never delivers non-resident status, because the Statutory Residence Test (SRT) measures UK workdays and ties, not calendar presence.

The trap sits in the significant-break test. A UK-resident in any of the three preceding tax years stays resident unless they work full-time overseas and have no significant break from that overseas work.

A significant break is 31 days or more with no overseas workday. On a two-on two-off rotation, every off-period back in the UK is a 14-day block with zero overseas workdays.

Do that for three consecutive rotations and you have a 31-day stretch in which no overseas workday falls. The test fails, and your employee is UK-resident.

Full PAYE on worldwide income follows, regardless of where the rig is or who flags the vessel.

The ties test then layers on. Accommodation, family, 90-day, UK-workday, and country ties: offshore workers typically meet three or four.

Anyone needing reliable non-resident status needs a rotation pattern redesigned around the SRT, not around the crew planner’s convenience.

Payoff: before you classify an offshore worker as non-UK-resident, build a 12-month rotation calendar against SRT days and ties.

If the calendar does not clear the test cleanly, run UK PAYE and let them claim SED or foreign tax credit downstream.

How do you run Appendix 5 payroll for a UK employee posted abroad?

When you send a UK-resident employee overseas for an extended assignment, the default is double taxation. UK PAYE applies because they remain resident; host-country tax applies because they are working on local soil.

Without a workaround the employee waits until self-assessment for a foreign tax credit.

HMRC’s Appendix 5 modified payroll is the workaround. You run real-time PAYE, but you offset an estimated amount of host-country tax against the UK PAYE liability each pay period.

At year-end the employee reconciles through self-assessment, and you file a final Appendix 5 return with HMRC’s Expatriate Team.

Three conditions to enter Appendix 5. First, a written agreement with HMRC before the first qualifying pay period. Second, the employee must be tax-equalised or tax-protected under the assignment policy.

Third, the employer must commit to operating modified payroll for the full assignment and to filing the reconciliation.

Your software needs to support the modification. Xero, Sage 50 Payroll, and BrightPay handle it through manual tax code overrides; PayFit and Pento need bespoke configuration raised with support. IRIS has a native Appendix 5 flag but still requires the HMRC agreement on file.

See our payroll software buying guide for assignment-ready shortlists.

NT (no tax) codes are the alternative when the employee becomes non-resident during the posting. The employer applies on form P85 or via a mutual agreement procedure.

Until HMRC issues the NT code in writing, keep running standard PAYE.

When does UK NIC follow an employee abroad, and when does it stop?

National Insurance follows a different geography from income tax and trips finance teams that assume they move together. Two regimes apply: the EU/EEA/Swiss coordination regime, and everything else.

For EU/EEA and Swiss postings, an A1 certificate keeps the employee inside UK NIC for up to 24 months. Your employer continues to pay Class 1 primary and secondary contributions, and the host country grants exemption.

Without the A1, host-country social security applies from day one, usually on top of UK NIC, leaving the employer with double contributions for every month until the certificate lands.

Article 16 of the UK-EU Protocol on Social Security Coordination allows an extension to five years by mutual agreement between HMRC and the host-country authority.

Apply early; six-month processing delays are common for Article 16 cases.

For non-reciprocal countries (most of the world outside the EU, a handful of bilateral exceptions like the US, Japan, South Korea), UK NIC continues for the first 52 weeks of a posting, then stops. The employee joins the host-country social security from week 53.

Class 1 primary continues for the employee; secondary liability sits with the employer until that 52-week mark.

For reciprocal-agreement countries, the bilateral convention sets the duration. US postings carry a 5-year certificate of coverage; Japan is 5 years; Canada varies by province.

Check the specific convention, not a general rule.

Scenario rule: budget A1 applications as a cost centre, not an afterthought. One missing A1 on a 12-month EU posting can wipe out the margin on the assignment through double employer contributions.

How does IR35 apply to offshore contractors?

Offshore contractors sit in an awkward space between PSC engagements and bureau-supplied crew. If you are a medium or large end-client supplying offshore personnel through a limited company, you are in scope of the off-payroll working rules regardless of the rig or vessel location.

Our off-payroll working guide covers the status determination process.

The UKCS regime layers on top. Even where IR35 would normally leave the contractor outside PAYE (genuine business on its own account), s.41 pulls UKCS earnings back into PAYE.

The end-client or the fee-payer in the contractual chain becomes the deemed employer for PAYE and Class 1 NIC purposes.

Status Determination Statements for offshore contractors need to address three vectors: control (rotation patterns and tool-box talks often indicate control), substitution (rig access vetting usually prevents unrestricted substitution), and mutuality of obligation (multi-rotation framework contracts lean towards mutuality).

Most rig-based PSC engagements land inside IR35.

For seafarers, the picture is closer to conventional IR35. Merchant seafarers operating through a PSC on a qualifying vessel can fall outside IR35 on facts, and the SED relief is then claimed by the contractor on their personal self-assessment.

Wind turbine installation crews are harder to place; the 2014 extension brought their earnings inside PAYE territory regardless.

Rule: treat every offshore PSC engagement as inside IR35 by default and let a documented status determination move it outside. Starting outside and being reassessed by HMRC is the expensive order to do it in.

What records does HMRC expect you to keep for offshore payroll?

Offshore payroll is a documentation-heavy regime because every relief and every allocation is evidenced by where the worker was on which day.

HMRC enquiry teams ask for specific records; you should have them ready on request.

For SED claims, keep crew lists, boarding manifests, port logs, and discharge books for each eligible period. ITEPA 2003 does not prescribe a single format, but HS205 expects a daily record reconciling to employer timesheets and to the shipowner’s voyage logs.

Keep it for four years after the tax year of the claim.

For UKCS workers, keep the licence operator’s site presence records, helicopter or vessel manifest extracts, rotation schedules, and the principal contractor agreement identifying the secondary NIC contributor.

HMRC’s Oil and Gas team runs random checks and will ask for cross-references.

For abroad postings, keep the Appendix 5 agreement, the A1 certificate (or its application receipt), the assignment letter, and a monthly calendar of workdays showing the country code per day.

Payroll software tends not to store this natively; most People Ops teams run it in a shared spreadsheet and reconcile monthly.

Our UK payroll operations guide covers the baseline record architecture.

For IR35 determinations, keep the Status Determination Statement, the supply chain map, and the fee-payer letter confirming PAYE operation downstream.

The end-client carries liability until a compliant SDS is passed down the chain.

Payoff: if you cannot produce a day-by-day location record per offshore worker on 48 hours’ notice, your offshore payroll is an enquiry away from arrears. Build the log before you need it.

Which payroll software handles offshore and assignment cases well?

Most UK payroll software handles the basics (PAYE, RTI, auto-enrolment) but few handle the offshore and assignment edge cases without heavy manual work.

Our reviews of IRIS Payroll, Sage 50 Payroll, and Cintra go into capability per provider.

The practical shortlist for multi-regime offshore payroll is short. IRIS and Cintra handle SED workflows natively (NT code management, HS205 reporting packs).

Moorepay and other bureau providers typically handle it through caseworkers rather than software, which works if you have fewer than 50 offshore workers and want human judgement in the loop.

For Appendix 5 modified payroll, you want a provider that has done it before. Cintra, IRIS, and a handful of boutique global payroll providers have the flag in their system.

Xero, BrightPay, and Pento are workable with manual overrides but need a payroll lead who understands the mechanics.

For A1 certificate tracking, no UK payroll product does this natively at the time of writing.

Most People Ops teams track A1s in their HRIS or in a spreadsheet alongside assignment letters, and reconcile against the payroll each month.

Scenario rule: if more than 10% of your headcount is offshore, seafarer, or on long overseas assignments, your payroll tool choice is driven by those cases, not by the 90% of domestic staff.

Shortlist on the edge cases.

What should a UK People Ops lead do next?

Offshore payroll is a domain where the upside of getting it right (SED relief, A1 savings, clean Appendix 5 operation) matches the downside of getting it wrong (PAYE arrears, double NIC, failed status determinations).

Three steps.

First, map every worker outside a standard UK office against the four regimes: SED seafarer, UKCS installation, abroad-posted UK employee, and inside-IR35 offshore PSC.

Most finance teams find the count is higher than they think once remote-work-abroad creep is included.

Second, pull the documentation baseline. Crew lists for seafarers, rotation schedules for UKCS, A1 certificates and Appendix 5 agreements for postings, SDSs for contractors.

If any category has gaps, fill those gaps before the next tax year boundary.

Third, match your payroll tool to the case mix. The right tool for a 300-strong UK-domestic business with two seafarers is not the right tool for a 200-strong business where half the crew rotates through North Sea rigs.

Our payroll software buying guide is built around exactly this kind of edge-case-first shortlisting.

Rule: offshore payroll mistakes compound quietly. Catch them at the regime-mapping stage, not at the HMRC enquiry stage.