Tax Joint Liability Derivation in Spain (Art. 42 LGT): Complete 2026 Guide and Differences with Social Security

What joint liability derivation under Art. 42 of the Spanish General Tax Act involves: cases, procedure, deadlines and defence against the AEAT. Comparison with joint liability under Art. 42 of the Workers' Statute before the TGSS: similar but very different.

A powerful tool of the Spanish Tax Agency you need to understand

Joint liability derivation in tax matters is one of the most powerful mechanisms available to the Spanish Tax Agency (AEAT) to collect unpaid debts. It allows a third party — director, partner, business successor or collaborator in a tax offence — to be held personally liable with their own assets for a tax debt that was not originally theirs.

It is regulated in Article 42 of the Spanish General Tax Act (LGT) and has become a daily tool used against entrepreneurs, freelancers, business heirs and individuals who, often without knowing, find themselves exposed to someone else's tax debt.

This article explains what it is, when it applies, how the procedure works and, above all, how to defend yourself. At the end, we compare it with joint liability under Article 42 of the Workers' Statute before the TGSS — analysed in detail in our [Social Security joint liability case won (Judgment 183/2026)](/blog/responsabilidad-solidaria-articulo-42-et-tgss): they look alike, but they are structurally similar yet very different in requirements, deadlines and defence strategy.

1. What is tax joint liability derivation?

It is the administrative act by which the AEAT declares that a person other than the principal debtor becomes liable for the entire tax debt, on the same footing as the original debtor.

Unlike subsidiary liability, the Tax Agency does not need to exhaust enforcement against the principal debtor or declare them insolvent: it is enough that the voluntary payment period has expired and the debt remains unpaid to initiate the file against the joint debtor.

2. Substantive and formal requirements

For the derivation to be legally enforceable, two layers must converge:

Substantive requirement: existence of one of the statutory cases in Art. 42 LGT (collaboration in an offence, business succession, concealment of assets, breach of seizure orders, etc.).

Formal requirement: the AEAT must follow a strict procedure with three mandatory steps:

  1. Hearing notice to the alleged liable party, with 15 working days to submit allegations.
  2. Reasoned resolution proving the facts and culpability.
  3. Notification with payment slip indicating the deadline under Article 62.5 LGT.