Box 8TK: the tax credit on foreign income, explained simply
Box 8TK (form 2042 C) takes the total of your foreign-source income already taxed abroad that qualifies for a tax credit equal to the French tax: you pay no French tax on it, but it counts for the rate applied to your other income.
What is box 8TK for?
When a tax treaty uses the “credit equal to French tax” method, income taxed abroad must still appear in your French return: first in its nature box (for example 1AF for filer 1’s foreign salary, 1BF for filer 2), then the total in box 8TK.
France then computes a tax credit exactly equal to the French tax on that income: the net effect is that you pay no French tax on it, but it raises the rate applied to your other French income and enters your reference tax income (RFR).
This is the mechanism that applies notably to Luxembourg salaries of cross-border workers living in France, and to German salaries of people without cross-border-worker status.
Classic mistakes
Forgetting annex 2047: any foreign-source income goes through form 2047 first, then carries over to the 2042. Box 8TK without a 2047 is inconsistent and attracts requests for justification.
Confusing tax credit with exemption: some foreign income is instead EXEMPT with a progression clause (effective-rate method) — a different mechanism with different boxes (e.g. 1AC for a Geneva salary). You don’t get to choose: it follows from the treaty between France and the country concerned.
Deducting the foreign tax yourself from your declared salary: the tax credit neutralizes double taxation, not a manual subtraction.
Fill it in without mistakes
Our guided flow “French cross-border return (2042 + 2047)” computes the exact amount for 1AF then 8TK from your salary certificate, and gives you every box ready to copy-paste.
Frequently asked questions
Is 8TK income really untaxed in France?
You pay no French tax on this income (the credit cancels it exactly), but it raises the rate applied to your other French income and your reference tax income — which can affect RFR-based benefits or exemptions.
Do I need to attach proof of the tax paid abroad?
Not systematically when filing, but keep your salary certificate or foreign tax assessment: the administration may ask for them, especially in the first years.