The Gipuzkoa Tax Authority in the Basque Country announced that The TicketBAI obligation does not exempt taxpayers from complying with SII requirements. However, it is clarified that the data sent by TicketBAI will be understood as filling in the same matching fields that correspond in the SII exclusively with the ledger of invoices issued required for the SII.
The remaining data that have not been completed must be completed within the established deadlines to comply with the SII through the appropriate web services enabled. Therefore, taxpayers issuing TicketBAI must continue to send the information corresponding to the rest of the SII ledgers (received invoices, fixed assets, and certain intracommunity supplies).
Source: https://www.gipuzkoa.eus/es/web/ogasuna/impuestos/iva/sii/
More information about TicketBAI: Spain: Spain: New Timelines for the Adoption of TicketBAI in the Basque Country | Sovos