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The 15% rule of the simplified regime: 5 rules so you do not pay IRS on expenses you did not justify
Step Inside Accounting · Practical guide
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1. Understand the rule
For services (coefficients 0.75 and 0.35), the Tax Authority compares two things:
- 15% of what you invoiced in the year;
- the total of the expenses the law accepts for this purpose (rule 2).
If the expenses reach 15%, nothing happens. If they fall short, the difference is added to your taxable income. The rule does not apply to sales of goods or to restaurants and hotels.
2. Know which expenses count
These count towards the 15%:
- a fixed deduction of €4,587.09 in 2026 – or, if higher, your compulsory Social Security contributions that you have not deducted in any other way;
- salaries and other pay you give to staff;
- rent for the space where you work, with an invoice – if it is the home where you also live, only 25% of the rent counts;
- 1.5% of the tax value of a property you own where you carry out your activity (4% for alojamento local and hotels) – if it is also your home, only 25% of that amount counts;
- other business expenses with an invoice in your NIF: materials, electricity, water, communications, transport, insurance, rents and hire, professional association fees, travel and accommodation;
- purchases made in other countries for your activity.
Mixed expenses only count at 25%. When an expense serves both your personal life and your work, only 25% of the amount counts. This mainly affects people who work from home: the rent (or the tax value of the home, if you own it), electricity, water, internet and mobile phone. For example, if you pay €900 a month in rent (€10,800 a year) for the home where you live and work, €2,700 (25%) counts towards the 15%.
3. Up to around €30,500, the fixed deduction is enough
The fixed deduction of €4,587.09 covers, on its own, 15% of a turnover of up to €30,580.60. Below that amount, you do not have to justify anything else.
Above it, you have to add other expenses. If you pay Social Security contributions as normal, they can cover a good part of the difference. The most exposed case is that of people who are exempt from contributions – for example, because they are also employed – and invoice more than €30,580.60.
4. Classify your invoices in e-fatura by the end of February
Expenses with invoices only count if they are linked to your activity in e-fatura. When an invoice has your NIF, you have to say whether it is a business or a personal expense, and whether you use it fully or only partly for work. The deadline is the end of February of the following year.
If you forget, you can still declare the amounts in the self-employed annex of your IRS return. In that case, you must keep the invoices so you can show them if the Tax Authority asks.
5. Do the maths before you file your IRS
In the IRS simulator, the addition appears in your category B taxable income. Before you file your return, check:
- how much 15% of what you invoiced is;
- how much the fixed deduction (or your contributions) and the expenses you linked to your activity add up to;
- whether there are invoices still to classify or classified as personal by mistake.
An expense that is not linked to your activity counts as if it did not exist.
Example
Pedro is a programmer (coefficient 0.75). He is employed and is therefore exempt from Social Security as a self-employed worker. In 2026 he invoices €36,000 on recibos verdes:
- 15% of €36,000: €5,400;
- fixed deduction: €4,587.09;
- missing: €812.91.
If Pedro does not link any other expense to his activity, the €812.91 is added to his taxable income: €27,000 (75% of €36,000) + €812.91 = €27,812.91.
But in March Pedro bought a €1,000 computer that he uses only for work. If he links that invoice to his activity in e-fatura by the end of February, his expenses reach €5,587.09, above the €5,400, and his taxable income stays at €27,000.
Team tip
Always use your NIF for business expenses and go into e-fatura every three months to classify them – in February there are always forgotten invoices. If you invoice more than €30,000 a year and are exempt from Social Security, talk to us in January: there is still time to see what is missing.
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This article is for information only and does not replace professional advice. Figures and rules are those in force at the date of publication and may change.
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