a) Technical documentation that has changed.

Technical Import Guide CAU V3.13
Additional Information Import CAU GENERAL V3.16

Technical Guide for Customs Declarations for Low-Value Imports H7 V3.18

The variations are indicated in each modified technical document in its corresponding version.

b) modification of schemes in CAU import declaration.  
See list of modified schemes in version V3.13 - versioned -.

Can be seen at:

HEADQUARTERS: 

Tax Agency: Technical Guides - Submission of the Single Administrative Document ( SAD )
Web Services (agenciatributaria.gob.es).

c) Definitive closure of the current PreCau duo.

See news published on June 4, 2024 (H1 publication of technical documentation and calendar). This details the date of 10/14/2025 as the final and irreversible closing date for the current PreCau due date for the submission of new full or simplified declarations.

c) Email for inquiries: H1.info@correo.aeat.es