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IRS Payments on Account

The rate fell from 76.5% to 65%, and only the share of your tax that came from self-employment counts.

All four figures are from the year before last: for the 2026 instalments, they are the 2024 ones. They all appear on that year's assessment notice. The assessed tax is the figure left after tax credits, except the disability credit.

Each instalment (July, September, December)
€412
Total for the year
€1,236
Category-B share of income (RLB ÷ RLT)80 %
Tax attributable to category B€2,400.00
Formula base, after withholdings€1,900.00
Total under the previous 76.5% rule€1,455
Saved by the cut to 65%€219
You may withhold, interest free€247.20
Minimum to pay to stay in the margin€988.80

Only part of your assessed tax enters this calculation. Because category B accounts for this percentage of your net income, that is the share of the assessment the formula uses. Someone with only category-B income puts the whole assessment in, which is why calculations that apply the percentage to the full amount produce a higher figure.

The rate in force is 65%. Up to the 2024 instalments article 102 read 76.5%, and the Lei n.º 45-A/2024 of 31 December cut it; the 2026 State Budget kept it at 65%. Because most articles published on the subject predate 2025, they still explain the old rule.

The calculator applies the formula in article 102 of the Portuguese Income Tax Code and does not replace the assessment notice, which is where the tax authority states the official amount of each instalment. Out of scope: working out the assessed tax and its credits, determining net category-B income, corporate payments on account, and the exact compensatory interest of paragraph 6, which depends on a day count.

Educational estimate based on the figures you enter. It is not tax advice.

The calculation starts two years back, not last year

Article 102(2) of the Portuguese Income Tax Code requires the tax assessed "do penúltimo ano", the year before last, and that word is the first thing almost everyone reads too quickly. The 2026 instalments come out of the 2024 return filed in 2025, not out of the 2025 one. The reason is practical: the 2025 assessment is only finalised in the summer of 2026, after the first instalment has already fallen due, so the law steps back a year to have a settled figure. The consequence is that an unusually good or unusually bad year only reaches your instalments two years later, which is why so many people are surprised by the notice they receive. Anyone in their first or second year of activity usually has no assessment for that reference year, and therefore no payments on account at all.

Only the category-B share counts, and that is where most calculations go wrong

The formula in paragraph 2 does not apply the percentage to the whole assessment: it applies it to C × (RLB ÷ RLT) − R. That fraction is the part of the tax attributable to category B. Someone who invoices as a freelancer but also has a salary, a pension or rental income had their tax generated by all of those together, and only the part that came from the independent activity enters the payments on account. For a taxpayer whose total net income was 25,000 € and whose category B contributed 20,000 €, the ratio is 80%, so a 3,000 € assessment enters the calculation as 2,400 €. Someone with only category-B income has RLB equal to RLT, the ratio is 100% and the whole assessment goes in. Summaries that say "65% of your tax" are only right in that last case.

Tax already withheld is deducted, and often covers the whole thing

The R in the formula is the total tax withheld during the reference year on category-B income, and it is subtracted after the ratio has been applied. This has an effect worth anticipating: anyone who invoices companies, and therefore suffers withholding on nearly every invoice, has already been paying tax through the year, and it is common for those withholdings to equal or exceed the tax attributable to category B. When that happens the base is zero and there are no payments on account at all, however high the income. The opposite is equally true and is the case that usually catches people out: anyone invoicing mostly private individuals, or clients abroad, suffers no withholding at all, has R equal to zero and ends up with the largest instalments.

The rate fell from 76.5% to 65%, and almost nobody wrote it down

Until the 2024 payments on account, article 102(2) set the total at 76.5% of the formula. The Lei n.º 45-A/2024 of 31 December, the 2025 State Budget, replaced that figure with 65%, and the 2026 State Budget left it alone. The Portal das Finanças serves both versions side by side, which allows a word-by-word comparison: the percentage changes and nothing else does, not the formula, not the rounding, not the minimum. In practice that is 15% less on every instalment. Because almost every article published on the subject predates 2025, they still explain the 76.5% rule, and that is why this calculator also shows what the old rule would have produced: so you can see where the gap comes from between a figure you found elsewhere and the notice you received from the tax authority.

You may reduce or stop, but there is a 20% margin and then there is interest

Article 102(4) ends the obligation when the tax already withheld, together with instalments already paid, equals or exceeds the tax that will be due, or when category-B income simply stops. Paragraph 5 allows the instalment to be reduced whenever it exceeds the difference between the tax you believe is due and what you have already paid. Neither needs permission: the taxpayer decides, on the Portal das Finanças. The brake is in paragraph 6, and it is a generous but finite tolerance: if, because of that reduction or cessation, you fail to pay an amount greater than 20% of what would normally have been delivered, compensatory interest is due. The rate is the one in article 35 of the General Tax Law, which points to the civil statutory interest rate, and it runs day by day from the deadline of each payment. That is why the calculator shows how much you can withhold without entering that territory, and the minimum that keeps you inside the margin.

Worked example

Take a taxpayer with a 3,000 € assessment for the reference year, 500 € of tax withheld on category B, 20,000 € of net category-B income and 25,000 € of total net income. The category-B ratio is 80%, so the attributable tax is 2,400 €; less the 500 € withheld, the base of the formula is 1,900 €. 65% of that is 1,235 €, which divided by three and rounded up gives 412 € in July, 412 € in September and 412 € in December, a total of 1236 € for the year. Under the previous 76.5% rule each instalment would have been 485 € and the year would have come to 1,455 €: the 2025 change saves 219 €. If you decide to reduce the instalments, you may withhold up to 247.20 € without risking compensatory interest, meaning you must pay at least 988.80 € across the year.

Frequently asked questions

How are Portuguese IRS payments on account calculated?
By the formula in article 102(2) of the Income Tax Code: the total is 65% of C × (RLB ÷ RLT) − R. C is the tax assessed two years back, net of tax credits, RLB is that year's net category-B income, RLT is total net income and R is the tax withheld on category B. The result is split into three equal instalments, each rounded up to whole euros. With a 3,000 € assessment, 500 € withheld and a category B worth 80% of income, each instalment is 412 €.
When are they due?
By 20 July, 20 September and 20 December, under article 102(1). The tax authority states the amount on the assessment notice for the reference year and sends the payment document in the month before each deadline, but the obligation exists whether or not the document arrives. Unlike corporate tax, whose third instalment falls due on 15 December, all three dates here are the 20th.
Who is exempt from payments on account?
Three situations in practice. The first is paragraph 3: if each instalment would fall below 50 €, it is not payable. The second is a base of zero, which happens when the tax already withheld on category B equals or exceeds the tax attributable to that income, the common case for anyone invoicing companies. The third is having no assessment for the reference year, which covers anyone at the start of their activity. In addition, paragraph 4 ends the obligation for anyone who stops earning category-B income.
Why is my figure lower than the one I read elsewhere?
Almost certainly because the other calculation uses 76.5%. That was the rate in article 102 up to the 2024 instalments; the Lei n.º 45-A/2024 of 31 December cut it to 65% and the 2026 State Budget kept it there. The difference is around 15% on every instalment. The second most common cause is the other calculation applying the percentage to the whole assessment and skipping the RLB ÷ RLT fraction, which inflates the figure for anyone who also has a salary, a pension or rental income.
Can I pay less than the tax authority asks for?
You can, and you do not need permission. Article 102(5) allows the instalment to be reduced when it exceeds the difference between the tax you believe is due and what you have already paid, and paragraph 4 allows it to be stopped entirely when withholdings and instalments already cover the year's tax. The risk is paragraph 6: if that reduction means you fail to pay more than 20% of what would normally have been delivered, compensatory interest runs on the shortfall, day by day from the deadline of each payment. The calculator shows what that 20% margin is in your case.
What is the compensatory interest rate?
Article 35(10) of the General Tax Law states that the compensatory interest rate is equal to the statutory interest rate set under article 559(1) of the Civil Code, which is the civil statutory rate and has stood at 4% a year since 2003. The interest runs day by day from the deadline of each payment until the date the assessment is due, and article 102(6) adds two further conditions for it to be charged: that the reference year was assessed by 31 May and that the taxpayer remains in the same household.
Is this the same as company payments on account?
No, and the calculations differ. Corporate payments on account follow article 105 of the Corporate Income Tax Code, apply 80% or 95% depending on the previous year's turnover, start from the immediately preceding year rather than two years back, and the exemption is a 200 € base rather than 50 € per instalment. If that is the calculation you are looking for, it is the corporate payment on account calculator. This page is income tax only, for people with category-B income.
Are the calculator figures exact?
The formula, the 65% rate, the rounding up, the 50 € minimum per instalment and the 20% margin are those of article 102 of the Portuguese Income Tax Code as currently in force. The result is an educational estimate based on the figures you enter and does not replace the assessment notice, which is the document where the tax authority states the official amount of each instalment. If you do not know your assessed tax or how your income splits between categories, both figures are on the assessment notice for the reference year.

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Author: Thorben Rasmus Idel · Reviewed by: Nahar Geva · Last reviewed: 2026-08-17