Frequently asked questions about form 170 (fiscal year 2026 and subsequent years)

The 170 form has a monthly periodicity and its submission deadline will be the calendar month following the one to which the information refers.

The first declaration must be submitted in February 2026 with the data from January of that year.

Model 170 is submitted via WebService. Even so, the Tax Agency offers a WS client for small taxpayers (less than 10,000 records per submission), which allows the submission of a file of taxpayers.

If material errors are detected (e.g., incorrect IBAN), the erroneous records can be modified or cancelled.

Modifying a record completely replaces the data in the previous record. Therefore, if Communication Type L1=A1 (modification) all fields of the record must be submitted, not just the changed fields.

In case of cancellation, Communication Type L1= A2 (registration cancellation), it is sufficient to indicate the Declared Registration ID + Declarant ID + Fiscal Year, without needing to resend the entire content of the registration.

The communication type will always be A0, except when that IdRegistro is to be modified or deactivated in the same period due to errors in the information initially reported in the same period.

The “Type of communication” A1 (modification) or A2 (deletion of record) is only used for the correction of errors in previously declared records.

A single submission can include records that correspond to different types of communication: additions, modifications or removals.

Yes. They must correct the declarations for all periods affected by the error.  Each period is independent; for example, if an error in the January declaration is corrected, the error in the already submitted February declaration will not be automatically corrected; both must be corrected.

The response message includes an overall result of the submission, which can be accepted (if there are no errors in any record), partially accepted (when there are accepted and rejected records) and rejected (when all records have been rejected).

The error codes can be found at the following link:

Error documentation attachments - Developers (agenciatributaria.es)