Lorena Vidal is a self-employed translator in Burgos. In April 2025 she sent her gestor (the Spanish term for the adviser or agency that handles tax paperwork) all the documents for her 2024 income tax return by email, including her bank's certificate for the sale of some investment funds that left her with a gain of 16,300 €. The gestor filed the return without that gain. In 2026 the Agencia Tributaria, the Spanish tax agency, notifies her of a proposed assessment: 3,100 € of tax, 190 € of interest and, shortly afterwards, the start of penalty proceedings for 1,550 €. Lorena is clear that the mistake was not hers. What she wants to know is who pays for each item and how to claim.
Before Hacienda, the taxpayer is you
The Ley General Tributaria, Spain's General Tax Law, has no concept of "the adviser's error". The taxpayer is the person who carries out the taxable event, and it is that person the authorities regularise and penalise. When a professional files a return in your name, they act as your representative: article 46 of that law allows you to act through a tax adviser and, where filing is electronic, provides that the person filing acts with the representation needed in each case. For the Agencia Tributaria, the incomplete return is Lorena's return.
That is why the assessment of the tax, of the interest and, where applicable, of the penalty is addressed to her. No communication to the gestor replaces Lorena's own reply, and the deadlines run against her.
What someone else's error can change before Hacienda
The tax is owed in any event: the gain existed and had to be declared. Where the professional's error can carry weight is in the penalty, because penalties require fault. Article 179.2.d) excludes liability when the taxpayer has taken "the necessary care in complying with tax obligations".
Lorena can argue that she handed all the information over in time to a professional and that the omission did not depend on her. It has to be said that the outcome of this argument is uncertain. Administrative doctrine and the courts do not always accept that delegating to an adviser rules out the taxpayer's fault, especially when the error was easy to spot on reviewing the draft or the return filed. A great deal depends on Lorena being able to prove what she handed over and when; the April email is her best evidence.
The email with the certificate attached, the engagement letter, the gestor's invoices and any message confirming receipt of the documents are the basis both of the defence against the penalty and of the later claim. It is worth gathering and keeping them before telling the professional that a claim will be made.
The claim against the professional: what has to be proved
The relationship with the gestor is a contract for services. Article 1101 of the Civil Code obliges those who, in performing their obligations, are guilty of "wilful misconduct, negligence or delay" to compensate for the damage. Article 1104 defines negligence as the failure to exercise the care required by the nature of the obligation, taking into account the circumstances of the persons, the time and the place. From a professional who charges for preparing returns, the care proper to that trade is expected.
For the claim to succeed, Lorena has to prove four elements:
- The engagement. That the gestor took on the preparation of her 2024 income tax return. Invoices and emails are normally enough.
- The breach. That the gestor had the information and did not include it. The April email with the certificate attached is decisive.
- The damage. What specific financial loss she suffered because of that failure.
- The causal link. That the damage is due to the professional's error and not to some other cause.
As it has no special time limit, the claim becomes time-barred five years after performance could be demanded (article 1964.2 of the Civil Code). In practice it is best not to cut it fine: evidence deteriorates, and professional liability insurers impose their own deadlines for reporting a claim.
Which part of the cost can be claimed
Not everything Lorena pays to Hacienda, as the Spanish tax office is commonly called, is damage attributable to the gestor. The distinction is this:
| Item | Amount in the example | Does Lorena pay it to Hacienda? | Can it be claimed from the gestor? |
|---|---|---|---|
| Tax omitted | 3,100 € | Yes | In principle no: she owed it anyway |
| Late-payment interest | 190 € | Yes | Debatable: it compensates for the time she had the money |
| Penalty | 1,550 € before reductions | Yes, if her defence fails | Yes, if it is due to the error |
| Cost of the defence | Depends on the case | — | May be claimed as consequential damage |
The tax is not usually damage because Lorena would have had to pay it if the return had been correct. There are different cases, in which the professional's error causes the loss of a tax benefit that did exist, such as a missed deadline for an exemption or an option that had to be exercised in the return. There the difference in tax may indeed be the damage, although each case is argued on its own.
Reducing the damage also protects the claim
The 1,550 € penalty is not the final figure. With the 30 % reduction for agreement and the 40 % reduction for prompt payment in article 188, paying it on time without appealing would leave it at:
- 1,550 × 0.70 = 1,085 €.
- 1,085 × 0.60 = 651 €.
This raises a strategic decision. If Lorena appeals the penalty to defend her diligence, she loses the 40 % and, if she loses the appeal, the damage will be greater. The gestor could argue that part of that damage is due to Lorena's decision to appeal. If she pays with the reductions, the damage she claims is smaller but easier to sustain. How assessment, penalty and reductions fit together is explained in is the penalty appealed separately from the assessment?, and the effect of signing or arguing against the proposal in I have received a proposed assessment.
A middle way, when the gestor acknowledges the error, is to agree in writing that they will bear the penalty and the interest before deciding whether to appeal. If they have professional liability insurance, the insurer should be notified as soon as possible.
The order of the steps
- Reply to Hacienda on time. The procedure does not wait for the dispute with the gestor.
- Gather the proof of the engagement and of the documents handed over.
- Argue diligence against the penalty, if there are grounds for it.
- Tell the gestor in writing about the error and the loss, and ask for their insurance details.
- Decide whether to pay with the reductions or appeal, bearing in mind the effect on the claim.
- Quantify the damage once the penalty is final, and claim it.
If you are in this situation, you can send the notification from Hacienda and the emails with your gestor through the letter-from-Hacienda form. The reply to the Agency is prepared separately from the claim against the professional, although the two are coordinated.
A more general approach, with no request involved, is in my adviser got it wrong: who answers to Hacienda?. If the error is discovered before Hacienda detects it, voluntary correction changes the cost completely: this is explained in the difference between a notice letter and a formal request.
Defence against regularisations arising from third parties' errors is described on the Salama Tax page on letters from Hacienda.