1. What falls due on 15 December

Article 104(1)(a) CIRC requires corporate tax to be paid in three instalments on account, due in July, September and on 15 December of the same year the taxable profit relates to. Companies whose tax period differs from the calendar year (article 8(2) and (3)) pay in the 7th month, the 9th month and on the 15th day of the 12th month of that period.

Note the asymmetry: the first two instalments fall due on the last day of the month, the third on the 15th. It is a common and expensive diary mistake, because under article 104(5) CIRC compensatory interest starts running immediately if the payment misses its deadline.

If the company's taxable profit in the previous period exceeded EUR 1,500,000, the third instalment of the additional payment on account of the state surcharge falls due on the same date: article 104-A(1)(a) CIRC points expressly to the rules in article 104(1)(a), and article 105-A sets the applicable rates (2.5%, 4.5% and 8.5% by band of the previous period's taxable profit).

2. Where the instalment amount came from

Before deciding whether to stop the payment, it helps to know what it was calculated on. Under article 105(1) CIRC, the base is the tax assessed under article 90(1) for the immediately preceding tax period, net of the deduction in article 90(2)(e) — that is, net of withholding tax that cannot be offset or refunded.

The rate applied to that base is:

• 80% where the previous period's turnover was EUR 500,000 or less (article 105(2));
• 95% where it exceeded EUR 500,000 (article 105(3)).

In both cases the result is split into three equal amounts, rounded up to whole euros. That is why the third instalment is normally identical to the other two: it is not a true-up, just the final third of a calculation based entirely on the past.

Check the figures before you decide: HVR's corporate tax payments on account calculator works out the base, applies the 80% or 95% rate and returns all three instalments. For the regime as a whole, see our guide to corporate tax payments on account in 2026.

3. The only two lawful ways out

3.1. Skipping the third instalment entirely (article 107(1))

The wording is unambiguous: where the taxpayer establishes, from the information available to it, that the amount already paid on account equals or exceeds the tax that will be due on the taxable base for the period, it may refrain from making the third payment on account.

Three points about that rule. First, it applies only to the third payment — the July and September instalments cannot be stopped this way. Second, the comparison is between what has been paid and the tax that will be due, not between what has been paid and the instalment. Third, the test is the information available to the taxpayer, which means the decision rests on the current year's accounting records, not on a cash-flow hunch.

3.2. Capping the instalment at the shortfall (article 107(3))

Where a company will owe tax, but less than the three instalments combined, it does not have to choose between paying everything and paying nothing. Article 107(3) allows the third payment to be capped at the difference between the total tax the taxpayer believes is due and the amounts already paid, with the preceding paragraphs applying with the necessary adaptations — which means the same exposure to compensatory interest.

4. The 20% test and compensatory interest

This is where the decision pays off or bites back. Article 107(2) CIRC provides that where the annual return for the year shows that, as a consequence of suspending the third instalment, an amount more than 20% greater than what would normally have been paid went unpaid, compensatory interest is due from the end of the period in which the payment should have been made until the deadline for filing the return, or until the date the self-assessment is paid if earlier.

Read what that means in practice. The margin for error is not zero: the law tolerates a deviation of up to 20% of the instalment that would have been due. But the interest window is not short — it runs from 15 December to, at the outer limit, 31 May of the following year (article 120(1) CIRC), or to the date the self-assessment is paid if that comes first.

The practical conclusion: suspending the instalment is not a December cash-flow call, it is an early year-end close. Anyone who suspends without closing the books through November is gambling.

5. What the estimate has to cover

The most frequent mistake is to estimate only the tax on profit and forget everything that follows in the assessment. The estimate should capture:

• Corporate tax on the taxable base. For tax periods beginning during 2026, the rate in article 87(1) and (5) CIRC is 19%, under article 3(2) of Law no. 64/2025 of 7 November. For taxpayers qualifying as an SME or a small mid cap under the annex to Decree-Law no. 372/2007, the rate on the first EUR 50,000 of taxable base is 15% (article 87(2), applicable to periods beginning on or after 1 January 2026), falling to 12.5% for entities qualifying as a startup that also meet the conditions in article 2(1)(f) of Law no. 21/2023 of 25 May (article 87(8)).
• Autonomous taxation. It is assessed under article 89 and, under article 88(23) CIRC, no deductions whatsoever are made against the total assessed, even deductions arising from special legislation. It forms part of the total tax in the return and therefore part of the article 107 comparison.
• The state surcharge, where taxable profit exceeds EUR 1,500,000 (article 87-A), at rates of 3%, 5% and 9% by band.
• Carried-forward tax losses — and their ceiling. The deduction in any period cannot exceed 65% of that period's taxable profit (article 52(2) CIRC). Companies counting on losses to wipe out the tax routinely forget this brake.

One 2026-specific point that changes estimates: the 10 percentage point uplift in autonomous taxation rates for taxpayers reporting a tax loss (article 88(14) CIRC) does not apply in the 2026 tax period where, under article 95(5) of Law no. 73-A/2025 of 30 December, the taxpayer made a taxable profit in one of the three preceding periods and filed the returns required by articles 120 and 121 CIRC for the two preceding periods; or where 2026 is the period in which activity began, or one of the two following periods.

6. Companies that never face the decision

For some companies the question does not arise. Under article 104(4) CIRC, taxpayers are exempt from making payments on account where the tax for the reference period used to calculate them is below EUR 200. What counts is not the profit but the previous year's tax — the same figure that forms the base in article 105.

In the other direction, article 104(7) rules out the balancing payment and the refund where the amount involved is below EUR 25.

One lingering confusion is worth clearing up: the special payment on account in article 106 CIRC was repealed by Law no. 12/2022 of 27 June, with effect, under article 329(2) of that Law, for tax periods beginning on or after 1 January 2022. What falls due on 15 December is the ordinary payment on account, not the old special one.

7. Checklist before 15 December

1. Close the books through November and project December. Without that there is no information available to the taxpayer in the sense of article 107(1).
2. Work out the estimated taxable base, with the foreseeable add-backs and deductions and the 65% ceiling in article 52(2).
3. Compute the year's autonomous taxation on vehicles, entertainment expenses, per diems and mileage not rebilled to clients, and undocumented expenses, under article 88.
4. Add the state surcharge where it applies, and check the additional payment on account.
5. Compare the estimated total tax with the July and September instalments already paid.
6. Run the 20% test: if the gap between what you plan not to pay and what would be due comes anywhere near that threshold, pay or cap rather than suspend.
7. Keep the working paper behind the estimate, dated. That is what justifies the decision if the tax authority asks.

Where the numbers are tight, the prudent reading is article 107(3): cap rather than suspend. You pay less now and cut your exposure to compensatory interest.

Frequently asked questions

Can I simply not pay the third instalment on account?

You can, if the information available to you shows that the instalments already paid equal or exceed the corporate tax that will be due on the period's taxable base. That is article 107(1) of the Corporate Income Tax Code (CIRC). It is not a free choice: there has to be a reasoned estimate behind it.

What is the exact deadline for the third instalment in 2026?

15 December 2026, under article 104(1)(a) CIRC. Companies whose tax period does not match the calendar year pay on the 15th day of the 12th month of that period.

What if I want to reduce the amount rather than skip it?

Article 107(3) CIRC lets you cap the third instalment at the difference between the total tax you believe is due and the amounts already paid. The same rules as for a full suspension apply, with the necessary adaptations, including compensatory interest.

When does compensatory interest become payable?

When the annual return shows that, as a result of the suspension, an amount more than 20% greater than what would normally have been paid went unpaid. Interest runs from the end of the payment deadline until the deadline for filing the return, or until the date the self-assessment is paid if earlier (article 107(2) CIRC).

Do I have to notify the tax authority that I am suspending the instalment?

Article 107 CIRC requires no prior notice or application. The decision is the taxpayer's and feeds through to the final computation in the Modelo 22 return. That does not mean you can skip the paperwork: the estimate you relied on is what justifies the decision if the tax authority asks.

Does autonomous taxation count towards the estimate?

It should. The final settlement is the difference between the total tax computed in the return and the amounts paid on account (article 104(1)(b) CIRC), and autonomous taxation is assessed under article 89 with no deductions allowed against the total assessed (article 88(23)). A company with a tax loss can still owe tax purely through autonomous taxation.

Does the EUR 200 exemption apply here too?

Yes. Under article 104(4) CIRC, taxpayers are exempt from paying instalments on account where the tax for the reference period used to calculate them is below EUR 200. In that case there is no first, second or third instalment.

Sources and legal references

• Article 104(1)(a) CIRC — three payments on account, due in July, September and on 15 December.
• Article 104(4), (5) and (7) CIRC — exemption where the reference-period tax is below EUR 200; compensatory interest for late payment; the EUR 25 threshold.
• Article 104-A CIRC — payment of the state surcharge in three additional payments on account, on the article 104(1)(a) dates.
• Article 105(1) to (3) CIRC — calculation base and the 80% and 95% rates, split into three equal amounts.
• Article 105-A CIRC — calculation of the additional payment on account (2.5%, 4.5% and 8.5%).
• Article 106 CIRC — special payment on account, repealed by Law no. 12/2022 of 27 June (article 329(2)).
• Article 107(1) to (3) CIRC — limits on payments on account: suspending the third instalment, compensatory interest above 20%, and capping at the shortfall.
• Articles 87, 87-A, 88 and 90 CIRC — corporate tax rates, the state surcharge, autonomous taxation and assessment.
• Article 52(2) CIRC — the 65% of taxable profit ceiling on the deduction of carried-forward losses.
• Article 3(2) of Law no. 64/2025 of 7 November — the 19% rate for tax periods beginning during 2026.
• Article 95(5) of Law no. 73-A/2025 of 30 December — disapplication of the article 88(14) uplift in the 2026 tax period.
• Texts consulted in the Corporate Income Tax Code as published by the Portuguese Tax and Customs Authority at info.portaldasfinancas.gov.pt.