# Cambio de base de cotización y comunicación de rendimientos previstos (autónomos)

> “Cambio de base de cotización y comunicación de rendimientos previstos (autónomos)” is a procedure of the Seguridad Social (TGSS, Social Security). In 2026 it has 6 deadlines in its calendar: the first falls due on 28 February 2026 and the last on 31 December 2026.

- Address: https://misobligaciones.com/en/modelos/reta-base/
- Reviewed on: 2026-09-21
- Language: en

## In a nutshell

- **Filed with:** the Seguridad Social (TGSS, Social Security)
- **For those taxed in:** All of Spain
- **How often:** otra
- **Deadlines in 2026:** 6, from 28 February 2026 to 31 December 2026
- **Official calendar consulted on:** [21 September 2026](https://sede.agenciatributaria.gob.es/Sede/ayuda/calendario-contribuyente/calendario-contribuyente-2026/calendario-anual.html)

## Who files it

*Text from the official source, in Spanish*

Autónomos del RETA que prevén que sus rendimientos netos del año cambian de tramo. Hasta seis cambios al año.

## Exceptions and special cases

*Text from the official source, in Spanish*

- Al darse de alta se comunican los rendimientos previstos en el propio alta (Import@ss).

## All its deadlines

Each row is a deadline from the official calendar: the last day to file. When that day falls on a Saturday, Sunday or public holiday, the calendar already moves it to the next working day.

| Period | Last day | Day |
| --- | --- | --- |
| Efectos 1 de marzo de 2026 | 28 February 2026 | Saturday |
| Efectos 1 de mayo de 2026 | 30 April 2026 | Thursday |
| Efectos 1 de julio de 2026 | 30 June 2026 | Tuesday |
| Efectos 1 de septiembre de 2026 | 31 August 2026 | Monday |
| Efectos 1 de noviembre de 2026 | 31 October 2026 | Saturday |
| Efectos 1 de enero de 2027 | 31 December 2026 | Thursday |

Every deadline of the year, month by month: [2026 tax calendar](https://misobligaciones.com/en/calendario-fiscal-2026/).

## Official links

Where it is filed, its instructions and, if there is one, the file format for importing it. All on the website of the Seguridad Social (TGSS, Social Security).

| For | Official link |
| --- | --- |
| Instructions and help | [Bases, tramos 2026 y solicitud de cambio de base](https://www.seg-social.es/wps/portal/wss/internet/Trabajadores/CotizacionRecaudacionTrabajadores/10721/10724/1320/1322) |

## Frequently asked questions

### When does “Cambio de base de cotización y comunicación de rendimientos previstos (autónomos)” fall due in 2026?

According to the official calendar of the Seguridad Social (TGSS, Social Security): Efectos 1 de marzo de 2026, by 28 February 2026; Efectos 1 de mayo de 2026, by 30 April 2026; Efectos 1 de julio de 2026, by 30 June 2026; Efectos 1 de septiembre de 2026, by 31 August 2026; Efectos 1 de noviembre de 2026, by 31 October 2026; Efectos 1 de enero de 2027, by 31 December 2026.

### Who does “Cambio de base de cotización y comunicación de rendimientos previstos (autónomos)” apply to?

According to the Seguridad Social (TGSS, Social Security): “Autónomos del RETA que prevén que sus rendimientos netos del año cambian de tramo. Hasta seis cambios al año.”

### What happens if “Cambio de base de cotización y comunicación de rendimientos previstos (autónomos)” is paid late?

If the returns were filed on time, the surcharge is 10% if you pay within the month after the due date and 20% afterwards; if they were not even filed, 20% or 35% (art. 30 of the Ley General de la Seguridad Social, the General Social Security Act). The details are in [the guide to missed deadlines](https://misobligaciones.com/en/fuera-de-plazo/).

### Does Mis Obligaciones do this procedure for me?

No. Mis Obligaciones suggests it in your calendar with the reason, takes you to its official page and reminds you a week before and the day before. The filing is done by you, or your gestoría (tax adviser’s office), on the website of the Seguridad Social (TGSS, Social Security).

> This is information copied from official sources to help you find your way, not tax advice: your case may have exceptions. Check it on the authority’s website or with whoever advises you.

## Official sources

- [2026 tax calendar for Mainland Spain and the Balearic Islands](https://sede.agenciatributaria.gob.es/Sede/ayuda/calendario-contribuyente/calendario-contribuyente-2026/calendario-anual.html) — Agencia Tributaria
- [Bases, tramos 2026 y solicitud de cambio de base](https://www.seg-social.es/wps/portal/wss/internet/Trabajadores/CotizacionRecaudacionTrabajadores/10721/10724/1320/1322) — Seguridad Social