German engineers come to Vietnam in a distinctive rhythm: installation and commissioning projects stretch over many months but are split into short trips of a few weeks each. That rhythm makes the two 183-day clocks — one in domestic law, one in the treaty — run completely out of sync, and the common mistake is to use a single clock for both questions. This article analyses German experts; the shared residence framework sits in the companion articles in this section, where the French case has similar European documentation mechanics but different treaty terms and project practice.
1. Clock one: residence under Law 109/2025/QH15
Article 2 of PIT Law 109/2025/QH15 (applying from the 2026 tax period, replacing Law 04/2007/QH12) makes an individual a resident when he is present in Vietnam for 183 days or more in a calendar year or in 12 consecutive months from the first day of presence, or has a regular place of abode in Vietnam under a fixed-term home lease. A project engineer on many short trips may be non-resident by the calendar-year count yet still become a resident if the trips bunch into one rolling 12-month window. Residents declare worldwide income on the five-bracket scale (Article 9) with personal relief (Article 10: 15.5 million VND monthly for the taxpayer and 6.2 million VND per dependant); non-residents pay 20% on Vietnam-source income. Day counting must be done per rolling 12-month window from entry–exit stamps.
2. Clock two: the 183-day clause in the Vietnam–Germany treaty
The Vietnam–Germany double taxation agreement is in force; its dependent personal services article (Article 15) allows a German resident’s salary to be taxed only in Germany only if three conditions coincide, the time condition being presence in Vietnam not exceeding 183 days in the 12-month period concerned. The other two: the payer is not a Vietnamese resident, and the salary is not borne by a permanent establishment or fixed base in Vietnam. For installation projects, the third condition ties into a larger risk: if the German enterprise’s installation activity in Vietnam lasts long enough to constitute a project permanent establishment, not only does the individual treaty condition fail, the German enterprise itself incurs Vietnamese corporate income tax on profits attributable to that establishment. This is the fundamental difference from Korean experts working for an already-established subsidiary: on the German side, the individual question and the sending enterprise’s permanent-establishment question must be answered together.
3. German documents: residence certificate and project records
The central document is the certificate of tax residence (Ansässigkeitsbescheinigung) issued by the German tax office (Finanzamt) for the relevant year, together with the secondment or installation contract identifying who pays and who bears the salary, and site work logs as the basis for day counting. When claiming treaty exemption trip by trip, the employer needs the treaty-application notification to the Vietnamese tax authority, in which the 183-day figure must be presented on the treaty’s own 12-month basis rather than copied from the residence day-count. Recurring documentary defects in the German group are a residence certificate issued to the company instead of the individual engineer, and project records that track installation time by payment milestones instead of actual days of presence.
4. Risks that accumulate with project age
Risk in the German model grows with the project’s age. Early on, short trips sit safely below the treaty threshold; as the project slips, extends or enters a warranty phase, cumulative presence can cross 183 days within a 12-month window unnoticed, retroactively collapsing the exemption for that window. At the same time, the enterprise’s presence at the site may reach the threshold for a permanent establishment, triggering corporate registration and filing duties. Sound management is a “day budget” for each engineer and for the project itself from contract signing: remaining day allowance, warning points before the threshold, and a switch-over plan (registering for Vietnamese withholding) if the project overruns.
This article has been quality-reviewed by the FLAW AI Legal Council