Marina Ortiz is a self-employed designer in Gijón. In 2023 she invoiced 11,000 € to an agency in Amsterdam and, because of an error in her spreadsheet, those invoices never made it into her income tax return for that year. She found out in spring 2026, while preparing her 2025 return, and thought of the easiest solution: add the 11,000 € to her 2025 income and pay the difference there. "That way I declare it myself before they ask me for it," she told herself. That decision, which seemed the most honest, is one of the few that turn a voluntary regularisation into a penalty.
The general rule is clear and favourable: anyone who files and pays before there is a prior formal request pays a surcharge, not a fine. But the law attaches conditions to that rule, and each one has its trap.
The rule and the two articles behind it
Article 27 of the General Tax Act (Ley General Tributaria) governs the surcharges for filing late without a prior request, and it says that the surcharge excludes the penalties that could have been imposed. Article 179.3 completes it: anyone who voluntarily regularises or corrects an incorrect return incurs no liability for the infringements committed when filing it.
The same article 179.3 adds a warning that hardly anyone reads: that exemption is without prejudice to the infringements that may be committed by filing the new returns late or incorrectly. In other words, the regularisation also has to be done properly.
First trap: declaring it in the wrong year
Article 27.4 requires late self-assessments to identify expressly the period to which they refer and to contain only the data for that period. Putting 2023 income into the 2025 return breaches both. And article 191.6 says what happens then: failing to pay on time tax later included in a self-assessment that does not meet those requirements will always be a minor infringement.
Let us assume, purely for the example, that the extra 11,000 € in 2023 means 2,900 € of additional tax, and compare the two routes.
Correct route: a supplementary return for 2023, filed in September 2026.
- Tax on the supplementary return: 2,900 €.
- More than twelve months have passed since the end of the filing period, so the surcharge is 15 %: 435 €.
- With the 25 % reduction under article 27.5, if she pays the tax on filing and pays the surcharge on time: 326.25 €.
- Late-payment interest from the end of those twelve months.
Easy route: adding it to 2025.
- Hacienda, as the Spanish tax office is commonly known, can assess 2023 with its 2,900 € and late-payment interest from the end of the original filing period.
- Minor infringement under article 191.6: a fine of 50 %, 1,450 €.
- With the 30 % reduction for agreement under article 188.1.b): 1,015 €.
- With the 40 % reduction for payment on time without appealing under article 188.3: 609 €.
- And the 2025 return still has to be corrected, since it now contains 11,000 € that do not belong there.
Besides the cost, the easy route leaves a record. Article 187.1.a) increases serious and very serious penalties where, in the previous four years, there was another final penalty of the same kind.
Second trap: returns that carry no money
Some returns, filed late, do not give rise to a surcharge because there is no tax to pay: information returns, registration returns and self-assessments that come out at zero or with a refund. For them, article 27 does not apply but article 198 does, which makes failing to file them on time an infringement even when there is no financial loss. Coming forward does not wipe out the fine: it halves it.
| Return filed late | Ordinary penalty | Penalty if you come forward |
|---|---|---|
| Self-assessment or return with no financial loss | 200 € fixed | 100 € |
| Registration return | 400 € fixed | 200 € |
| Information return supplying data, per person or entity | 20 € per item of data, minimum 300 € and maximum 20,000 € | 10 € per item, minimum 150 € and maximum 10,000 € |
Paragraph 2 of the same article adds a useful rule: if an incomplete return was filed on time and a supplementary or replacement return is later filed late, without a request, there is no infringement for the incomplete one and only what was declared late is penalised, at half.
Anyone who holds accounts abroad and discovers they should have filed Modelo 720, the return on assets abroad, years ago faces a reduced penalty, not an exemption. It should be calculated before filing, because in returns with many items of data half the amount can still be significant.
Third trap: filing without paying, or paying only part
Filing the self-assessment without paying does not turn the delay into an infringement: article 27.3 provides that, in that case, the enforcement-period surcharges on the unpaid amount are added to the late-filing surcharge. It is more expensive, but it is still not a penalty. Regularising half-way is another matter: declaring the income Hacienda already knows about and keeping quiet about the rest. The omitted part remains an unregularised failure to pay, which can be penalised if it is discovered later.
If the problem is that you cannot pay it all at once, a deferral requested on filing is the orderly route, and its effect on the reduction of the surcharge is set out in how much the surcharge for filing late is.
Fourth trap: believing you are still first
Coming forward means filing before there is a notified action aimed at regularising that same item and period. If Marina had received, before filing, a formal request about her 2023 income tax, the supplementary return would no longer have the effect of article 27. The rule in article 191.6 itself recalls this in its final paragraph: it does not apply where what was included relates to items and periods for which a request had already been notified.
An information letter does not have that effect, nor does a request for information sent to a third party, while an unopened electronic notification may well have it. The list of doubtful situations is in the guide on what counts as a prior formal request.
If you have something outstanding and would like us to review it before you file, send the returns concerned through the regularisation form. We will tell you which period each item of income belongs to and what it would cost to do it properly.
A case with no surcharge at all
Since Law 11/2021, article 27.2 provides for a situation with no surcharge. If Hacienda regularises one year for certain facts and you, within the six months following that assessment, correct the same facts in other periods of the same tax, no surcharge is charged on those other returns. The conditions are strict: paying in full, not appealing the assessment or asking for its rectification, and no penalty having resulted from the tax authorities' regularisation. If one fails, the surcharge is charged without further formality.
It does not apply to Marina, because nobody has assessed anything for her. But it matters for anyone who receives an assessment for one year and knows the same mistake is repeated in the following ones.
What Marina should file
A supplementary 2023 income tax return with the 11,000 € and the related expenses, identifying the tax year. A 2025 return without that income. And since those invoices went to a company in another Member State, a check on whether they were included in Modelo 349, the EU transactions return, for their quarter: if not, that information return is also outstanding, with the reduced penalty of article 198 seen above. The difference between surcharge and penalty, explained as a whole, is in surcharge, interest and penalty.
Regularisations of one or several tax years, with the cost calculated before filing, are described on the page on voluntary disclosure with Salama Tax.