The first quarter must close in April. Third sector entities that are obliged to file tax returns can do so from 1 April to 20 April inclusive, or up to 15 April if you want to pay by direct debit. The forms to be submitted to the Tax Agency during this quarter are explained below. If you need help filing taxes with your bank or other tax issues, our financial service will be happy to help you. Declaration on Personal Income Tax withholdings The following forms must be submitted to declare the withholdings referring to Personal Income Tax withholdings.