The 15% Expense Proof Rule, Simplified Regime in Portugal (2026)

How it works

Under the simplified regime, for the professions listed in the Art. 151.º CIRS table, the tax authority assumes 25% of your services revenue covers business expenses (the 0.75 coefficient means 75% is taxable, 25% is assumed costs). Other services use the 0.35 coefficient. The 15% rule covers both (Art. 31.º n.º 13 names alíneas b) and c)).

There's a catch: you must prove at least 15% of your gross services income in documented expenses. If you fall short, the gap between your documented expenses and the 15% threshold gets added back to your taxable income.

This is a services-only rule. Sales of goods (vendas) use the 0.15 coefficient and are not subject to it.

What counts toward the 15%

Expense type	Counts?	Notes
Business expenses with NIF in e-fatura	Yes	Must be classified as professional expenses
Social Security contributions	Up to a point	Count toward the leg only up to 10% of your gross services (Art. 31 nº13 a) CIRS)
Specific deduction (~€4,587.09 (2026))	Yes	Applied automatically by AT. It's the lower bound of the automatic leg, not an addition on top of Social Security
Personal expenses (health, education)	No	They are personal deductions (deduções à coleta), not part of the 15%
Portuguese invoices without your NIF	Only once you register them	An invoice issued without your NIF is not linked to you in e-Fatura. You can still register it yourself as the buyer, using its QR code or ATCUD, by the end of February of the following year (Art. 78.º-B n.º 3 and n.º 5 CIRS, applied by Art. 31.º n.º 15 a)). Once registered and classified, it counts
Foreign supplier invoices	Depends on what you bought	Never captured by e-Fatura. EU purchases where you self-assessed the VAT (reverse charge) and goods imported from outside the EU go in Anexo B quadro 17A, campo 17002, added alongside the e-Fatura figure (see which expense figure AT uses). An EU purchase where the supplier charged its own VAT (a hotel abroad, for example) and services from outside the EU, such as a US software subscription, are open questions and may count nowhere. Foreign invoices do not belong in quadro 17C. Keep originals and payment proof for 10 years (Art. 52 CIVA).

Which expense figure AT uses

By default, AT uses what it already holds. That means the invoices that carry your NIF on e-fatura and that you have classified as wholly or partly professional. The classification is your job: you validate and classify each invoice in e-Fatura by the end of February of the following year (Art. 31.º n.º 15 a) CIRS). An invoice you never classified is not counted.

You can swap that figure for your own, but only in one place. In Anexo B of your IRS return (Modelo 3), quadro 17C asks whether you want to declare your personnel, rent and other business expenses instead of the ones communicated to AT. Tick campo 01 (sim) and AT uses only the totals you enter in that quadro. The e-Fatura figure for those expenses is ignored, not topped up.

So it is all or nothing. If you tick campo 01, the quadro must hold your full totals, including the invoices e-Fatura already had. Enter only the ones AT was missing and you have just discarded all the rest. Leave campo 02 (não) ticked and AT keeps using its own figure.

Ticking campo 01 changes which figure AT uses. It does not waive the rule that other business purchases count only when their invoices were communicated to AT or issued on the Portal. A supplier invoice that was never communicated, or a foreign one, does not become admissible by being typed into quadro 17C.

When is it worth doing? When AT's computed figure is wrong because communicated invoices, payroll filings or electronic rent receipts were missed. It cannot make costs count that were never communicated to AT. The risk is on you: what you declare replaces AT's numbers, and you must still be able to prove every amount (Art. 31.º n.º 16 CIRS, with the general burden of proof in Art. 128.º). If AT asks for proof, it recomputes the 15% test without the amount you cannot prove, and the resulting shortfall against 15% is what gets added back to your taxable income. If e-Fatura already looks right, leave campo 02 alone.

EU purchases where you self-assessed the VAT (reverse charge) and goods imported from outside the EU are separate. They go in quadro 17A (campo 17002) and are added alongside the e-Fatura figure, with no switch to tick. How an EU purchase that carried the supplier's own VAT, or services bought from outside the EU, should be treated is not settled, so check with an accountant before relying on them.

The math

The automatic coverage is a greater-of, not a sum. It is the higher of two things: the fixed specific deduction (dedução específica), or your Social Security counted up to 10% of your gross services. They do not add together.

Example: €40,000 in services income

• 15% threshold: €6,000 (0.15 × €40,000)
• Specific deduction: ~€4,587.09 (2026) (applied automatically)
• Social Security: ~€5,990 for the year, but it counts toward the 15% only up to 10% of your gross, which is €4,000 here

Because the capped Social Security (€4,000) is below the specific deduction, the automatic coverage is the ~€4,587.09 (2026) floor, not the two combined. That leaves you about €1,413 short of the €6,000 threshold. To close it, document real business expenses (equipment, software, professional services) before 31 December. Anything you can't document is added back to your taxable income.

This is an estimate to show the mechanism. Confirm your exact figures for your own income and Social Security situation.

Who usually needs to document extra

Because Social Security counts toward the 15% only up to 10% of your gross, the automatic coverage is capped. In 2026, below roughly €30,580 in services income, the specific deduction alone meets the 15% threshold, so you're covered with nothing to document. Above that, most services freelancers need real documented expenses to close the gap, and the higher the income, the larger the gap left open.

A few situations make the gap wider:

First-year freelancers. A first-ever registration does not contribute to Social Security until the first day of the 12th month after the start date, so the only automatic coverage is the ~€4,587.09 (2026) specific deduction. On roughly €30,580 in services income that exactly meets the 15% threshold. Earn more than that in year one, and you document the difference with real business expenses.

Higher earners. The 15% threshold climbs with every euro of income. Social Security counts only up to 10% of your gross, and only where it is larger than the specific deduction, so it never keeps pace with the threshold. The amount you need to document keeps growing above the break-even point.

Goods sellers (0.15 coefficient) are not subject to this rule at all.

How to track it

The only way to know where you stand is to track your documented expenses throughout the year. Finding out you're short when you file your IRS in June means it's too late to do anything about it for that tax year.

December is the last chance to make business purchases (equipment, software, training) that count toward the current year's 15% threshold.