Double taxation treaty
(DTT, or double tax agreement) is a bilateral treaty that allocates taxing rights between two countries so the same income is not fully taxed twice. For employers, treaties govern where salaries, director fees and business profits are taxed, and underpin the 183-day rule and permanent-establishment thresholds.
The rules at a glance
| Treaty concept | What it decides |
|---|---|
| Residence tie-breaker (Art. 4) | Which state treats a dual resident as its taxpayer |
| Employment income (Art. 15) | Whether the host state taxes salary — the 183-day test lives here |
| Permanent establishment (Arts. 5/7) | When local presence makes business profits taxable |
| Relief method (Art. 23) | Exemption vs credit for the residence state |
| Mutual agreement procedure | How the two states resolve conflicts |
How do double taxation treaties work in 2026?
Most treaties follow the OECD Model: each income type has an allocation article — employment income (Article 15), business profits (Article 7), directors’ fees, pensions, dividends — assigning primary taxing rights to one state and requiring the other to relieve the overlap by exemption or credit.
For mobile employees the core is Article 15: the work state may tax employment income unless the stay is short (the 183-day test) and the employer and costs stay outside that state. For companies, Articles 5 and 7 decide when local activity crosses into a taxable permanent establishment.
When should employers check the treaty?
Three routine situations:
- Assignments and remote workers abroad: the treaty decides when host taxation starts and whether shadow payroll is needed.
- Dual-resident employees: tie-breaker rules (home, centre of vital interests, habitual abode) fix a single treaty residence — see tax residency.
- Sales and delivery activity abroad: contract-concluding staff can create a permanent establishment long before an office exists.
Treaties do not harmonise social security — that is the job of EU Regulation 883/2004, A1 certificates and bilateral totalisation agreements, which run on separate rails from income tax.
Common mistakes
- Assuming relief is automatic: credits and exemptions must be claimed, usually with residency certificates and day-count evidence.
- Reading the OECD Model instead of the treaty: bilateral texts deviate exactly where it matters — check the specific articles.
- Forgetting social security: treaties cover income tax; contributions follow separate coordination rules and totalisation agreements.
- Ignoring the economic employer doctrine: cost recharges can hand taxing rights to the host state regardless of day counts.
Using treaties without getting burned
The practical employer mistake is assuming a treaty ‘fixes everything automatically’: relief usually needs claiming, day counts need evidence, and some treaties deviate from the OECD text exactly where you least expect. Check the specific bilateral treaty per assignment and keep travel records audit-ready. Access Financial structures assignment payroll around the applicable treaties in 60+ countries — request an assignment tax review.
FAQ
The questions clients and contractors ask us most.
What does a double taxation treaty actually prevent?
Juridical double taxation — the same person taxed on the same income by two states. The treaty allocates primary taxing rights per income type and obliges the residence state to relieve the remainder via credit or exemption. It does not equalise rates: you end up paying roughly the higher of the two burdens, not the lower.
How do I claim treaty relief on salary?
Typically through payroll and filings: the employer applies treaty-based withholding where domestic procedure allows (sometimes needing a residency certificate), and the employee claims credit or exemption in the residence-state return. Documentation — certificates of residence, day counts, employment contracts — decides whether the claim survives review.
What if two countries both claim tax residency?
The treaty tie-breaker resolves it in sequence: permanent home, centre of vital interests, habitual abode, nationality, and finally mutual agreement between the authorities. The outcome fixes which state taxes worldwide income and which only source income — a determination worth documenting before a dispute, not during one.