The 2023 financial year has been opened in the personal income tax WS integration environment:

https://ws.ia.aeat.es/wlpl/iniinvoc/es.aeat.dit.adu.suap.irpfws.IRPFXMLI3SOAP

The documentation updated with the new message schemes can be consulted at:

https://www2.agenciatributaria.gob.es/static_files/common/internet/dep/aplicaciones/es/aeat/suap/docu/Especificaciones_SW_SCSP_JAV3_IRPF.pdf

For the tests, the NIF of the holder must be used: 99999357A.