Yes, the Agència Tributària de Catalunya (ATC) is the Catalan tax agency. It’s completely separate from the national Agencia Tributaria (AEAT) and handles taxes that are managed by the Generalitat de Catalunya — the regional government.
You’ll deal with the ATC when it comes to things like vehicle tax, inheritance and gift tax, and donations or money transfers between individuals. So if someone gives you a car, or your parents transfer you a large sum of money, you’re expected to declare that to the ATC, not to the AEAT.
They also handle things like certain environmental taxes, tourist taxes (if you rent out property), and gambling duties. The rules can vary a bit from the rest of Spain, so if you’re based in Catalonia, make sure you’re checking the ATC’s guidelines — not just the national ones.
You can access their services online, and like the national agency, they accept things like digital certificates, idCAT, and Cl@ve PIN for logging in. It’s a separate system, but just as important to stay on top of. Ignoring it won’t make it go away — and late declarations can lead to fines, even if you weren’t aware you needed to file in the first place.