How it works

irsplit runs the same calculation twice for your household, once as a joint return and once as two separate returns, and compares the result.

Joint or separate

Since 2015, couples file separately by default. Married couples and partners in a união de facto can choose to file jointly instead, one year at a time. Both of you have to choose it in the return.

Filing jointly adds up both incomes, halves the total, works out the tax on that half and doubles it (the "quociente conjugal"). When one of you earns much more than the other, the higher earner's income is taxed at lower rates, and joint filing usually costs less. When you earn about the same, the two options usually come out level. Deductions also work differently: with separate returns, each of you gets half of the household limits and half of what the children are worth.

IRS Jovem

If you are 35 or under, part of your employment and freelance income is exempt for your first ten years of earning as a non-dependant: all of it in year one, 75% in years two to four, 50% in years five to seven and 25% in years eight to ten. The exempt amount is capped at 55 times the IAS each year. There is no degree requirement any more. The exempt income still counts when the rate is worked out for the rest, and you have to choose the scheme on the return.

What else the estimate includes

• The specific deduction for employees: a fixed amount, or your social security contributions if they are higher.
• The "mínimo de existência", which removes tax on lower incomes.
• Deductions for dependants, general family expenses, health, education, rent, care homes, invoice VAT and PPR, each with its own rate and limit.
• The overall limit on several of those deductions, which gets lower as income rises.
• The solidarity surcharge above €80,000 of taxable income.

The rates and limits come from the IRS code (CIRS) for the year you pick: 2025 or 2026 income. Where the tax office has not yet published its own figures for a year, we compute them from the law and say so in the result.

What it leaves out

Freelance (category B), pension, rental and investment income; ascendants, disability, alimony, domestic work and pre-2011 mortgage interest. If any of those apply to you, use the result as a rough guide and check the Portal das Finanças simulator before you submit.

An estimate, not advice

irsplit is a calculator. It does not know everything on your return, and it is not a tax adviser. The figure that counts is the one the tax office calculates. If something looks wrong, tell us.