5.11.4 Option to opt in voluntarily

Taxpayers who voluntarily wish to opt for the SII may do so at any time, maintaining their quarterly settlement period.

The option is exercised through form 036 (boxes 143 and 532), being included from the day following the end of the settlement period in which said option was exercised, being required to remain in it throughout the calendar year. Once the above deadline has passed, you can resign using form 036, in the month of November prior to the start of the calendar year in which it is to take effect. An extraordinary deadline for opting out of the SII for the 2026 fiscal year is established, until February 16, 2026. (New for fiscal year 2026)