TLDR: If you are domiciled in France and your Luxembourg salary is exempt from income tax in France but taken into account for the effective rate, declare it in boxes 1AC to 1DC. Do not report it in box 8TI.
Boxes to fill in
Declare the salary in boxes 1AC to 1DC. Indicate it after deduction of mandatory social contributions and after offsetting the tax paid in Luxembourg.
After applying the expense deductions, the net income is taken into account to calculate the effective rate applicable to your taxable income in France and to determine your reference tax income.
Return no. 2047 and box 8TI
If you do not receive any other income from foreign sources, you do not have to file return no. 2047.
If you receive other income from foreign sources, you must file return no. 2047 for that income and report its amount in box 8TI. The salary declared in boxes 1AC to 1DC must not be reported in box 8TI.