The complementary self-assessment box on page 1 of form 200 shall be marked with an "X" when for the same tax period, another or other returns for this tax have been filed previously and the new return aims to pay the difference between the result of the previous return and that of the new or complementary return, or to reflect an amount to be refunded that is lower than the amount previously self-assessed.Therefore, the complementary self-assessment will have to include all the data requested in the form, incorporating those that are the object of the new self-assessment, in addition to those that were included in the original self-assessment and in the successive self-assessments, where applicable.
When the taxpayer ticks the complementary self-assessment box, he/she must then enter the number of the receipt number of the previous self-assessment of the complementary self-assessment, which appears on the payment or refund document for the latter.
In addition, the result of the previous self-assessment must be entered in the section "Net amount to be paid or refunded (boxes 00621 and 00622)" on page 14 bis of form 200, the result of the previous self-assessment.
In the event that the original self-assessment had been paid, should complete the boxes  and  "Complementary:Result to be paid from previous self-assessments corresponding to tax period 2021" on page 14a of form 200 with the amount to be paid resulting from this self-assessment.
However, if the original self-assessment had resulted in a refund, in the boxes  and  "Complementary:Refunds agreed from previous self-assessments corresponding to tax period 2021" on page 14a of form 200, only the amount whose refund has been made by the Administration shall be entered.If the refund has not been agreed or made by the Administration, zero should be entered in the box corresponding to that Administration.
A tener en cuenta:
The taxpayer may submit a complementary self-assessment when the amount to be paid is higher than the previous self-assessment or the amount to be refunded is lower than the amount previously self-assessed.In other cases, if the taxpayer considers that the self-assessment has harmed his legitimate interests in any way, he may request the rectification of the self-assessment in accordance with the procedure established for this purpose.