On a part-time contract the company cannot decide on its own how many hours you work. It can only ask for complementary hours if you have agreed to them in writing, with limits on percentage and notice, and overtime is generally forbidden. If you have spent months doing “a little extra” that does not appear on your payslip, this page will help you check whether you are owed money.
Part-time means working fewer hours than a comparable full-time colleague
Article 12.1 of the Estatuto de los Trabajadores defines it like this: the contract is part-time when fewer hours per day, week, month or year have been agreed than those of a comparable full-time worker. That comparable worker is someone in your company and workplace, with the same type of contract and doing identical or similar work. If there is none, the working time in the collective agreement (convenio colectivo) applies or, failing that, the maximum legal working week.
It can be permanent or fixed-term, in the cases where the law allows that type of hiring (article 12.2).
A part-time contract must be in writing and state the hours
Article 12.4.a requires the contract to be in writing and to state the ordinary hours of work per day, week, month or year, and how they are distributed. If any of this is missing, the contract is presumed to be full-time, unless the company proves the services were part-time.
You have the same rights as a full-time worker, recognised proportionally to the time worked where their nature allows it (12.4.d). And if your day is split, there can only be one interruption, unless the collective agreement says otherwise (12.4.b).
Complementary hours only exist with a written agreement
Complementary hours are those worked in addition to the ordinary hours agreed. Article 12.5 sets specific conditions:
| Rule | What it says |
|---|---|
| Agreement | Only if expressly agreed, in writing |
| Minimum hours | At least 10 hours a week, calculated annually |
| Maximum in the agreement | 30% of ordinary hours; the collective agreement can set another percentage, between 30% and 60% |
| Notice | At least 3 days, unless the agreement sets less |
| Pay | As ordinary hours; they count for contributions and benefits |
| Withdrawal | With 15 days notice, after one year, in three situations |
If the company breaks these rules, your refusal to work the hours, even if agreed, is not a disciplinary offence (12.5.f).
There is a second type: voluntary hours
Separately from the agreement, on permanent part-time contracts of at least 10 hours a week, the company can offer you voluntary complementary hours at any time. They cannot exceed 15% of your ordinary hours, extendable to 30% by collective agreement (12.5.g). Saying no carries no penalty. These hours do not count towards the percentage of the agreement.
An example with numbers
Laura works 20 hours a week, half of a 40-hour full-time week, with a signed complementary-hours agreement and €12 gross per hour.
| Item | Calculation | Result |
|---|---|---|
| Maximum in the agreement (30%) | 20 × 0.30 | 6 hours a week |
| Maximum if the collective agreement raises it to 60% | 20 × 0.60 | 12 hours a week |
| Voluntary hours (15%) | 20 × 0.15 | 3 hours a week |
| Maximum with 30% agreement plus voluntary | 20 + 6 + 3 | 29 hours a week |
| A week with 6 complementary hours | 6 × €12 | €72 gross |
The sum of ordinary and complementary hours, voluntary ones included, cannot exceed the legal limit of part-time work defined in article 12.1; in other words, you can never end up doing a full-time week this way. In the example, 29 hours is below 40. And the company must tell you the exact day and time at least three days in advance.
No overtime, except in emergencies
Article 12.4.c forbids part-time workers from doing overtime, except under article 35.3, which covers hours needed to prevent or repair accidents and other extraordinary and urgent damage. What you work above your agreed hours is complementary time, not overtime. Without an agreement, it cannot be demanded.
To compare with the full-time case, see overtime in Spain: limits and pay. Article 35.2 reduces the maximum overtime in the same proportion for people working fewer annual hours.
Working-time records protect you
A part-time worker’s hours are recorded day by day and totalled each month. With your payslip, the company must give you a copy of the summary of all hours that month, ordinary and complementary, and keep those summaries for four years (article 12.4.c). If it does not keep the record, the contract is presumed to be full-time, unless proved otherwise.
If the reason for temporary employment or a succession of contracts is in doubt, check when a temporary contract becomes permanent in Spain.
That has a practical consequence: keep the monthly summary. If one month shows an hour fewer than you worked, you can claim the difference. More on this in working-time record in Spain.
Why your case may be different
- Your collective agreement can change the percentages and the notice. This is the most common source of differences. Look for the section on complementary hours.
- The agreement can come before or after the contract. It does not matter when it is signed, but it must be a specific, written agreement.
- The minimum wage applies pro rata. If you work fewer hours, the minimum is paid in proportion, under article 1 of Royal Decree 126/2026. At 50% of full time, the monthly minimum would be €610.50 in 14 payments. The calculation is in minimum wage 2026 in Spain.
- Changing your hours is voluntary. They cannot move you from full-time to part-time, or the reverse, unilaterally, nor penalise you for refusing (12.4.e).
What to do if they ask for more hours than agreed
- Check whether you have a signed complementary-hours agreement, and how many hours it covers.
- Check you were given at least three days notice, or the period in your collective agreement.
- Ask in writing for the monthly summary of hours and check that they appear on your payslip.
- If there is no agreement, say you will only do them if you choose to, and ask for that to be put in writing.
This page is general information. If deadlines or money are at stake, speak to an employment lawyer (abogado laboralista) or a union.