Social charges
You can make sure that investment income is not subject to social charges twice
Investment income, including bank interest, that has already had French social charges taken off before it was paid out to you, should be listed in your declaration in specific boxes relating to the social charges (section 2, 2042) and in the boxes for declaring the actual amounts of income.
This is to make sure that this is not subject to social charges again on the income when declared.
Normally these amounts will be prefilled in your declaration, but you should check them.
Box 2BH is for kinds of income giving rise to a deductible part of the CSG social charge if you opt for the bands; 2CG is for gains not giving rise to deductible CSG and 2DF is for gains that always give rise to deductible CSG.
If you qualify for exemption from CSG/CRDS as an S1-holder, check if your bank is taking this off at source and if so, ask the bank if it can stop doing so.
Such incomes that only had 7.5% of prélèvement de solidarité taken should be prefilled at 2DG.