Óscar Medina has been giving private guitar lessons in Cádiz since 10 March 2026. He started with two students, then there were twelve, and he is paid by bank transfer. He did not register anywhere until 20 July, when a student asked him for an invoice for his company. He is now registered with Hacienda (the Spanish tax office) and in the RETA (the Social Security scheme for the self-employed) with a July date, has four earlier months of undeclared activity and is wondering whether he should say something or wait and see if anyone asks.
The answer has two sides, one with Social Security and the other with Hacienda. Neither is solved by hiding the earlier months, because transfers leave a trail and because voluntary regularisation is almost always cheaper than the one that comes after a formal request.
What the regulations say about registering out of time
Registration in the RETA must be filed before you start, at most sixty calendar days in advance, under article 32.3 of the affiliation regulations (Royal Decree 84/1996). When it is filed late, article 46.2.c provides that it takes effect from the first day of the calendar month in which the requirements were met. In other words, not from the day it is filed, but from the beginning of the month in which the activity started.
The same provision adds that contributions for the periods before registration was formalised will be payable and will count towards benefits once paid, "with the surcharges and interest that legally apply", unless they are time-barred. And the Tesorería (the Social Security treasury) must inform the Labour Inspectorate of registrations applied for out of time.
| Type of registration | When it takes effect |
|---|---|
| Registration on time (up to three a year) | The day the requirements are met |
| Registration on time from the fourth of the year | Day 1 of the month in which they are met |
| Registration out of time | Day 1 of the month in which they are met |
| Registration by the authorities | Day 1 of the month in which the activity is proved |
The base that applies to those months
The General Social Security Act has a specific rule for this case. Article 308.1.a, rule 5, provides that, for registrations made by the authorities and for the period between the start of the activity and the month in which registration is applied for, when it is applied for from the following month onwards, the monthly base will be the minimum of bracket 1 of the year's general table, unless the Inspectorate sets a higher one. And in those months the later regularisation based on actual earnings does not apply.
Put another way: Óscar cannot argue that he earned little in March in order to contribute on the reduced table. The months before registration are charged on that base, with no later adjustment.
Óscar's months, step by step
- Actual start of the activity: 10 March 2026.
- Registration filed: 20 July 2026, out of time.
- Effective date of registration: 1 March 2026, under article 46.2.c.
- Months before the application: March, April, May and June.
- Base for those four months: the minimum of bracket 1 of the 2026 general table, with no regularisation.
- From July: the provisional base chosen on registering, which can be regularised with actual earnings.
- The surcharge under article 30 of the Act is added to the four back contributions.
The surcharge depends on how and when they are paid. Article 30 sets it in steps: 10 % or 20 % when the person responsible met their reporting obligations on time, and 20 % or 35 % when they did not, depending on whether payment is made before or after the period given in the claim for the debt. A late registration in principle places the self-employed person in the second group, so you should not count on the lower surcharge.
It also affects the tarifa plana (the flat-rate contribution): the reduced contribution has to be requested on registering, and a registration filed months late makes it difficult for those earlier months to benefit from it. The Tesorería will decide on the information it has; it cannot be taken for granted.
Notification to the Labour Inspectorate opens the possibility of penalty proceedings under the Act on Infringements and Penalties in the Social Order (LISOS), with fines graded according to seriousness. There is no way of ensuring that proceedings will not be opened, or of what the amount would be. The only thing that can be said is that coming forward on your own initiative, with the months properly identified and the contributions paid, is a much better position than waiting for the activity to be discovered through a complaint or a data cross-check.
The Hacienda side
With Hacienda there are two separate problems. The first concerns the tax register: Modelo 036 should have been filed before the start. Article 198 of the General Tax Act penalises the late filing of register returns with 400 € and halves the fine if the return is filed without a prior request. In Óscar's case, if he files the tax registration with the real start date before Hacienda asks him for anything, the risk is that reduced amount, without prejudice to any other reductions that apply.
The second problem is one of substance: the income from March to June existed and must be declared.
- For IRPF (Spanish personal income tax), it goes into his annual return together with the expenses he can support. If he was required to make the instalment payment on Modelo 130, the payments for the first and second quarters are out of time.
- For VAT, private lessons may or may not be exempt depending on who gives them and on what terms, and that classification has to be made before filing anything. If they are not exempt, the earlier payments included VAT and it would have to be declared.
- Self-assessments filed late without a prior request carry the surcharge under article 27 of the General Tax Act instead of a penalty. The guide on the article 27 surcharge explains how it is calculated according to the delay.
The date shown on the 036 must be the real one. Putting July so that the earlier months "do not exist" turns a delay into an inaccurate return, and the transfer receipts contradict that date without any effort.
The order in which to put it right
The prudent sequence is as follows:
- Reconstruct the activity: students, dates, payments received and expenses from the first day.
- File or amend the 036 with the real start date and the correct heading, which you can check in what the IAE heading is.
- Check that the RETA shows the same start date, and notify it if not.
- Pay the back contributions as soon as they are claimed, so as not to move into the higher surcharge.
- File late the VAT and IRPF quarters that apply.
- Keep the whole file in case a request or an inspection report arrives.
If you are in this situation, you can send us the chronology and the payments received through the self-employed registration form. With that information the tax side can be put in order and what needs to be notified to Social Security can be identified.
When the activity was occasional
There is a nuance that should not be lost. The RETA requires habitual activity. Someone who gives three one-off lessons in a year may not be obliged to register with Social Security, although they must declare that income for IRPF. There is no income threshold laid down in the law that settles the question on its own; it is an assessment of the facts. In Óscar's case, twelve weekly students over four months can hardly be presented as something occasional.
Nor does it change anything to have started small. The obligation arises with the activity, not with the first month in which you earn enough. To avoid it happening again with another activity, the correct order is in Hacienda or Social Security: which comes first.
At Salama Tax we handle the tax side of these regularisations: the date in the tax register, the outstanding quarters and the annual return. We warn you of the risks of each step, but the outcome of penalty proceedings depends on the authority handling them and cannot be guaranteed in advance.