Moving people across borders is not just logistics—it’s trust. Japanese companies sending talent to the UK often promise certainty through tax equalisation. Modified UK payroll is the mechanism that makes that promise work in practice, and it’s meaningfully different from local UK payroll.

What modified UK payroll is

Modified payroll (often referred to as “Appendix 6 Modified PAYE”) lets employers operate UK PAYE fortax-equalised assignees using estimated, grossed-up earnings while guaranteeing the employee a net package and settling UK tax on their behalf. It typically runs as a shadow payroll alongside the employee’s home- country payroll, ensuring UK tax reporting without shifting the main pay processing out of Japan. HMRC frames this within expatriate tax equalisation—where the employer meets all UK income tax arising on cash and non-cash benefits while the employee receives a net entitlement.

How modified payroll differs from local UK payroll

• Purpose: Local payroll calculates UK tax on actual gross pay for UK employees; modified payroll exists to honour tax-equalised net promises for international assignees while meeting UK PAYE reporting obligations.
• Pay basis: Local payroll uses actual monthly earnings and benefits; modified payroll uses estimated grossed-up figures during the year, then corrects via an annual reconciliation.
• Tax bearer: In local payroll, the employee bears UK tax via PAYE; under modified payroll, the employer funds UK tax due under equalisation arrangements.
• Payroll location: Local payroll is processed in the UK; modified payroll commonly shadows the home- country (Japan) payroll while still operating UK PAYE for UK workdays and benefits.
• Compliance lens: Overseas employers with UK workers must address UK payroll obligations regardless of where the main payroll runs; modified payroll is the compliant route for tax-equalised assignees.

When Japanese companies should use modified payroll

• Tax-equalised secondments to the UK: If Japanese HQ guarantees a net salary and commits to paying UK tax for assignees, Appendix 6 modified payroll is the appropriate UK mechanism.
• Home payroll retained in Japan: When salary and benefits continue to be paid from Japan but UK reporting is required, a shadow modified payroll provides UK PAYE compliance without moving core pay processing.
• Complex benefits and allowances: Modified payroll can accommodate housing, cost-of-living, and other assignment benefits within estimated gross-ups, then true up at year-end.

Key compliance steps for Japanese employers

• Register the scheme: Set up an Appendix 6 Modified PAYE arrangement with HMRC for tax-equalised assignees and keep expatriate employee records aligned with HMRC expectations.
• Operate PAYE on estimates: Run UK PAYE during the year on estimated grossed-up earnings for each assignee, reflecting equalisation and assignment benefits.
• Annual reconciliation: Perform the end-of-year true-up to reconcile estimated vs actual earnings and benefits, settling any UK tax differences centrally as the employer.
• Coordinate globally: Align Japan payroll, UK shadow payroll, and assignment policies so net guarantees and UK compliance are consistently delivered.

Side-by-side comparison

Attribute	Modified UK Payroll (Appendix 06)	Local UK Payroll
Purpose	Tax-equalised assignees; UK compliance with net guarantees	Standard UK employees; PAYE on actual gross pay
Pay basis	Estimated grossed-up during the year; year-end reconciliation	Actual monthly earnings and benefits
Tax bearer	Employer pays UK tax under equalisation	Employee pays UK tax via PAYE
Payroll location	Shadow payroll in UK; core pay often remains in Japan	UK payroll only
Primary use case	International secondments with net pay guarantees	Domestic UK employment

Common pitfalls and tips

• Underestimating benefits: Ensure allowances, housing, relocation, and in-kind benefits are captured in estimates to avoid large true-ups.
• Fragmented ownership: Assign a single owner to coordinate Japan payroll, UK shadow payroll, and tax advisors—ambiguity creates compliance gaps.
• Late registrations: Register Appendix 6 early; delays complicate PAYE and year-end reconciliation.
• Policy mismatches: Align tax equalisation policy language with payroll mechanics (who funds what, treatment of bonuses, timing).

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