What the tax class changes
The class decides how the barème is applied, not the rates themselves. In class 1 the barème applies to the income as it is. In class 2 the income is halved, the barème applies to that half, and the tax is doubled. Class 1a has its own formula: the barème applies to the income minus a quarter of its gap to €79,380, and from €51,804 the rate on each extra euro is capped at 39%.
On the same taxable income of €60,000, base tax is €11,164 in class 1, €8,843 in class 1a and €3,997 in class 2. On €90,000 the spread widens: €22,864, €20,543 and €11,350. The first tax due moves the same way: it appears at €13,400 in class 1, €26,600 in class 1a and €26,650 in class 2.
These figures match the official 2025 tables to the euro: the income is rounded down to a multiple of €50, the tax to the euro, and a tax under €12 is not due.
Separate or collective taxation
The class a household lands in depends on its situation: marriage or a declared partnership taxed jointly for class 2, single parent, widowhood or being over 64 for class 1a, and class 1 otherwise. This comparison does not guess that situation: it puts the two calculations side by side and lets the gap be read.
The gap comes entirely from the difference between the two incomes. With €60,000 and €30,000, separate taxation gives €13,162 and collective taxation €11,350, a difference of €1,812. With €90,000 and €0 the difference rises to €11,514. With €45,000 and €45,000 it falls to zero: two equal incomes produce the same tax on both sides.
The reason lies in the barème itself. Splitting moves the total through a lower bracket, so it only pays when one of the two incomes is markedly higher than the other. With equal incomes there is nothing to even out, and the two calculations meet.
How to use the comparison
Four fields. The two incomes decide the gap. The country of residence and the share of Luxembourg-sourced income never touch the amounts: they feed the quasi-résident test, which follows a rule of its own.
All four parameters fit in the page address. The "Copy link" button gives a URL that reopens the same situation, incomes, residence and Luxembourg share included.
- Your income and your partner’s: treated as taxable income, €0 to €1,000,000 each.
- Country of residence: Luxembourg, Belgium or France, the corridor the engine covers.
- Luxembourg-sourced income: compared against the 90% threshold of the quasi-résident rule.
Reading the result
The big figure is the annual difference between the two regimes. The two chips above the chart carry the amounts themselves, and the two bars draw them: separate taxation on the left, collective taxation on the right. A zero difference gives two bars of the same height.
The figures on this page are base tax. The income tax calculator adds the employment-fund contribution and subtracts the salaried tax credit, so its amounts do not line up with these. This comparison measures a gap between two calculation methods, not a tax bill.
The household marginal rate, under the chart, is the rate of the bracket the total reaches in class 2. On €90,000 of combined income it is 32%. That is the rate at which one more euro of deduction would be valued once the household is taxed collectively.
Frequently asked questions
What is the difference between Luxembourg tax classes 1, 1a and 2?
Class 1 covers a single person with no children, class 1a single parents, widowed people and those over 64, and class 2 married or partnered couples taxed jointly. Class 2 halves the income, applies the barème and doubles the tax; class 1a applies the barème to a reduced income, with the rate capped at 39%. On €60,000 of taxable income, base tax is €11,164 in class 1, €8,843 in class 1a and €3,997 in class 2.
When is class 2 available?
For a married couple or one in a declared partnership taxed jointly. A widowed person, a single parent or someone over 64 falls into class 1a. Every other situation falls into class 1. The model applies those rules as written, and does not read the number of children beyond the move into class 1a.
Can a cross-border couple be taxed in class 2?
For a non-resident couple, class 2 runs through a request for collective taxation; it is not automatic the way it is for a resident couple. This comparison computes the gap that option would produce, it does not trigger it. Access to Luxembourg deductions follows a separate rule, the 90% of Luxembourg-sourced income test.
Separate or collective taxation: what actually changes?
Separate taxation applies the barème to each income in class 1. Collective taxation adds the two incomes and applies the class 2 barème, which halves that total before taxing it. The gap therefore depends entirely on the difference between the two incomes: €1,812 for €60,000 and €30,000, €11,514 for €90,000 and €0, and zero for €45,000 and €45,000.
What is quasi-résident status?
A non-resident with at least 90% of their income sourced in Luxembourg can ask to be treated as a resident for deductions. The 90% threshold is the one this comparison applies, and it changes neither of the two tax figures shown: it conditions access to deductions, not the barème.
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