The Japanese secondment model has a feature few other countries share: the expert remains on the Japanese parent’s payroll, with salary split into a “Japan salary” kept in the Japanese system and allowances and pay in Vietnam. At Vietnamese finalisation, the hardest question is not the tax rate but identifying the full taxable income of someone who has become a Vietnamese tax resident while half of his income sits outside the Vietnamese HR team’s view. This article analyses Japanese experts; the residence framework is shared with other nationalities, but the secondment payroll mechanics and Japanese documents have their own specifics, while the Korean and US cases are covered in neighbouring articles in this section.
1. Residence and the scope of income to declare
Under Article 2 of PIT Law 109/2025/QH15 (replacing Law 04/2007/QH12, applying from the 2026 tax period), a resident is present in Vietnam for 183 days or more in a calendar year or in 12 consecutive months from first arrival, or has a regular place of abode in Vietnam under a fixed-term home lease. Long-term Japanese secondees almost always qualify as residents, and residents must declare worldwide income: salary paid by the Japanese parent for work in Vietnam is declarable regardless of where it is paid. Residents are taxed on the five-bracket progressive scale in Article 9, with personal relief under Article 10 (VND 15.5 million per month for the taxpayer, VND 6.2 million per dependant). Short-term assignees below the residence threshold pay a flat 20% on Vietnam-source income with no relief instead.
2. The Vietnam–Japan treaty and the “borne by” test
The Vietnam–Japan double taxation agreement is in force; its dependent personal services article (Article 15) lets a Japanese resident’s salary be taxed only in Japan if presence in Vietnam does not exceed 183 days in the relevant 12-month period, the payer is not a Vietnamese resident, and the salary is not borne by a permanent establishment in Vietnam. For long-term secondments the 183-day condition already fails, so the treaty grants no exemption; its practical value lies elsewhere: the tie-breaker rules allocating residence where a person is resident in both states under domestic law, and foreign tax credit mechanics at finalisation. What must be examined closely is the “secondment fee” the Vietnamese subsidiary pays the Japanese parent: if that fee is in substance a recharge of the expert’s salary cost, the Vietnamese authority looks through the form to identify the individual’s income and the real cost-bearer.
3. Japanese documents: the papers that decide the file
Japanese experts’ finalisation files usually break on documents, not principles. Needed are: a Japanese tax residence certificate for the exact year (issued by the Japanese tax authority); the parent’s global payroll statement showing total income and Japanese income tax and social insurance withheld; the secondment agreement and assignment decision stating the cost-bearing mechanism; and the Vietnamese home lease supporting the regular-abode test. Japanese documents must be translated and legalised as tax administration requires; the HR team’s own summary translations are usually not accepted in place of full translations of the payroll figures. A practical trap: the Japanese corporate fiscal year ends in March, misaligned with Vietnam’s calendar tax year — payroll statements must be re-cut to the calendar year for Vietnamese finalisation.
4. Risks specific to the split-payroll model
The largest risk is under-declaring the Japan-paid portion for a resident expert: the Vietnamese authority reconciles the subsidiary’s personnel costs against the number of experts actually working, and undeclared income discovered this way attracts back tax, late-payment interest and under-declaration penalties. The second risk is duplicated burden: the expert finalises in Vietnam on worldwide income while Japan withholds on the same secondment salary, yet no foreign tax credit claim is filed at either end. The third is timing: an expert who ends the assignment and leaves mid-year without finalising on departure leaves the file hanging into the next period. The sound approach is an income map for each expert from the assignment decision onward — who pays, who bears, where declared, which documents prove it — updated whenever the payroll mechanism changes.
This article has been quality-reviewed by the FLAW AI Legal Council
