2.11 Supplementary declaration
The field corresponding to the supplementary declaration must be completed whenever, for the same tax period, another declaration or declarations for this tax have been previously submitted and the new declaration aims to pay the difference between the result of the previous declaration and that of the new or supplementary declaration, or to reflect an amount to be refunded that is lower than the amount previously self-assessed. Therefore, the supplementary declaration must include all the data requested in the model, incorporating those that are the subject of a new declaration in addition to those that were included in the original and, where applicable, subsequent declarations.
If you have marked the supplementary declaration key with an "X", you must then state the supporting document number of the declaration prior to the one it is supplementing, which appears on the payment or refund document.
If, on the other hand, the original declaration has produced an undue income or the taxpayer considers that it has harmed, in any way, his legitimate interests, he may request the return of the income or request the rectification of the declaration. Therefore, in such cases it is not appropriate to submit additional declarations.