Paula Serrano is a nurse in Zaragoza. She filed her 2024 income tax return in May 2025, it showed a refund of 640 € and she received the money in July. In September 2026, sorting out papers for a loan, she finds two things. The first is that in March 2024 she sold units in an investment fund at a gain of 1,100 € and did not declare it, because the bank sent the certificate to an old address. The second is that in the same year she paid 1,500 € into a pension plan and did not include that either, although it would have reduced her taxable base. One error works in favour of the tax office and the other in her favour. She wants to know whether she has to file two different documents, one to pay and one to claim.
Until recently the answer would have been yes. Today, for income tax (IRPF) and VAT, it is no.
Two systems that exist side by side
The General Tax Act (the Ley General Tributaria) contains two traditional routes. Article 122.2 regulates the supplementary self-assessment, which can only be used when the correction means more to pay or less to be refunded. Article 120.3 allows the taxpayer to ask for the rectification of a self-assessment that has worked against them, through a procedure developed by articles 126 to 128 of the Regulation on tax management and inspection.
But the same article 120.3 adds that, where the tax's own rules so provide, the rectification is to be made by means of a rectifying self-assessment. And that is what the regulations for the two taxes that are corrected most often have done:
| Tax | How it is corrected | Rule |
|---|---|---|
| IRPF (income tax) | Rectifying self-assessment, in either direction | Article 67 bis of the IRPF Regulation |
| VAT | Rectifying self-assessment, with some exceptions | Article 74 bis of the VAT Regulation |
| Taxes without that provision | Supplementary return if more comes out to pay; a claim for rectification if less does | Articles 122.2 and 120.3 of the General Tax Act |
The rectifying return serves to "rectify, complete or amend" the earlier one. If the final result is more to pay, the rules for a supplementary return apply to it. If it is more to be refunded, the refund is deemed to have been requested by the filing itself.
One exception remains in both regulations: if the only reason for the correction is that the rule applied breaches a higher-ranking one, the Constitution, European Union law or an international treaty, the route of the claim under article 120.3 can be followed. If that reason comes together with others, the others go through a rectifying return.
Paula's figures in a single return
For the example we will assume that her marginal rate on the general base is 30 %. The gain on the fund is taxed in the savings base, whose first band, adding the state and regional scales in articles 66 and 76 of the IRPF Act, is 19 %.
- Effect of the forgotten gain: 1,100 × 19 % = 209 € more tax.
- Effect of the pension plan contribution: 1,500 × 30 % = 450 € less tax.
- Net result: 450 − 209 = 241 € more to be refunded.
- The rectifying return is filed with all the correct figures and the final result is a refund of 881 €, of which she has already received 640 €. The difference of 241 € is deemed to have been requested.
As the overall result is in her favour, there is no amount to pay and, therefore, no basis for the surcharge in article 27. Under the old scheme, by contrast, she would have had to file a supplementary return for the 209 €, with a surcharge for filing it late, and a separate claim for the 450 €, and wait for it to be decided.
Article 67 bis requires "all the data" of the return to be included. If Paula files it with only the fund and the plan, everything else is treated as undeclared and the result comes out absurd. You start from the previous return and correct it.
The tax agency can later check the rectifying return like any other. A more favourable result does not prevent a review of the pension plan contribution, so it is worth keeping the certificate from the plan manager to hand.
When the money arrives, and with what interest
The refund that results from a rectifying return is processed as a refund arising under the rules of the tax. Article 120.3 of the Act sets the rule for interest: if six months pass from the filing of the rectifying return without payment having been ordered for reasons attributable to the Administration, the Administration pays late-payment interest without having to be asked.
It is different when what is refunded is an undue payment, that is, money that was overpaid. In that case article 32.2 requires interest to be paid from the date of the payment until payment of the refund is ordered. If Paula had paid on her return instead of receiving a refund, interest would run from the day she paid.
The deadlines that run without warning
| What you want to do | Until when | Rule |
|---|---|---|
| Correct in your favour | Four years from the end of the filing period for the return | Articles 66.c) and 67.1 of the General Tax Act |
| Correct in the tax office's favour without a surcharge | Within the voluntary filing period for the return | Article 122.1 of the General Tax Act |
| Correct in the tax office's favour with a surcharge and no penalty | Until a request is notified or the year becomes time-barred | Articles 27 and 179.3 of the General Tax Act |
For the 2024 return, whose filing period ended on 30 June 2025, Paula can correct it in her favour until 30 June 2029. After that day, the right to the refund becomes time-barred even if the reason is obvious.
There is a less well-known limit. Article 126.2 of the Regulation on tax management prevents rectification from being requested while a check covering that same obligation is under way. In that case, whatever needs correcting is argued within the procedure already open.
If you have a return to correct and are unsure of the route, you can send us the original return and what you have found through the voluntary correction form.
Three ways to correct badly
Correcting only the error that works against the taxpayer. Paula might be tempted to file only the pension plan. The rectifying return obliges her to declare everything correctly, and if she leaves out the fund knowing it exists, the new return is knowingly incorrect, with the penalty in article 191 in play and without the protection of article 179.3.
Applying the correction to one year without checking the others. If the bank's certificate was going to the old address, it is likely that something is also missing in 2023 or in 2025. An error of address or of approach rarely affects a single year.
Waiting for the next tax season. Some people believe the error can be put right "in the next return". It cannot: each year is corrected in its own return, and anything included in another year is just as wrong.
If the correction affects another form
Some errors do not stop at the income tax return. A badly issued invoice can affect VAT and income tax at the same time, and in VAT there are cases that article 74 bis excludes from the rectifying return, such as correcting VAT unduly charged to others. When several forms are corrected, it is advisable to do it at the same time and on the same basis, so that the figures fit with one another.
And if the mistake was not yours but that of whoever filed the return, as far as the tax office is concerned the correction is still yours. The claim against the professional is a separate matter, which we cover in my adviser made a mistake.
Corrections of earlier years, whether in your favour or against you, are handled through Salama Tax's voluntary correction service, where every open year is reviewed before the first one is touched.