Rectification of errors or omissions suffered in declarations already submitted
It may happen that, once the Personal Income Tax return has been submitted, whether it consists of a self-assessment or a duly confirmed draft declaration, the taxpayer notices errors or omissions in the declared data. The procedure for rectifying such anomalies is different, depending on whether the errors or omissions have caused harm to the Public Treasury or to the taxpayer themselves.
Errors or omissions to the detriment of the Public Treasury
The procedure for regularizing tax situations derived from errors or omissions suffered in declarations already submitted that have caused damage to the Public Treasury, is discussed in Chapter 18 in the section " Regularization through the presentation of complementary self-assessment ".
Errors or omissions to the detriment of the taxpayer
If the taxpayer improperly declared any exempt income, calculated amounts in excess of what was due, forgot to deduct any fiscally admissible expense or omitted any reduction or deduction to which he was entitled and, consequently, his legitimate interests have been damaged, may request rectification of said self-assessment in accordance with the procedure discussed in Chapter 18.
It is allowed to request the rectification of self-assessment of the Personal Income Tax through the tax return itself, when the taxpayer has made errors or omissions that determine a greater refund in their favor or a lower income, which may This rectification request must be made for the 2021 tax period, not only through Renta Web but also through the presentation programs developed by third parties.
Note: If the taxpayer wishes to request rectification of their self-assessment for the 2021 financial year, they must check box  of the declaration. Once marked, the self-assessment acts as a written request for rectification of the self-assessment, in accordance with the provisions of article 67 bis of the Personal Income Tax Regulations .