When one partner cuts back, incomes shift
When one partner in a marriage or civil partnership goes part-time, the ratio of the two salaries often changes significantly. The tax classes that suited you before may then lead to unnecessarily high or low monthly wage-tax deductions. This article explains the three options and works through an example.
The three combinations
IV/IV: both partners are taxed like single people. This suits couples who earn roughly the same.
III/V: the partner in class III receives double the basic allowance and pays much less wage tax, while the partner in class V pays more. This pays off each month when the salaries are far apart, as a rule of thumb at a ratio of about 60 to 40 or more.
IV/IV with factor: the tax office calculates a factor below 1 that distributes both partners' wage tax so that it roughly matches the actual annual tax (Section 39f EStG). This avoids large back payments and shares the burden fairly by income.
Example with part-time
Partner A earns €4,500 gross; partner B works part-time after the switch and earns €1,800 (transition zone). Both without children and without church tax, figures rounded under the 2026 rates:
With IV/IV, A keeps about €2,894 net and B about €1,377, together about €4,271 a month.
With III/V, A keeps about €3,239 and B about €1,201, together about €4,440 a month.
In this case III/V puts about €168 more into the account each month. Important: this is not a real tax saving, just a different distribution over the year. The actual income tax is assessed jointly for both partners with the tax return. Depending on the situation, this leads to a refund or a back payment.
Why the factor method is often fairer
With III/V, the partner in class V notionally bears a large part of the joint tax burden. Their net pay therefore looks smaller than their actual contribution to household income. This can distort the question of whether part-time "pays off". The factor method, by contrast, distributes the tax in proportion to the incomes. Both partners see a realistic figure on their payslip, and the back payment at the end of the year is usually small. You apply for the factor at the tax office, and it applies for up to two years.
The obligation to file a tax return
Couples who choose III/V or the factor method must file an income tax return. With III/V, set money aside for a possible back payment, especially if the partner in class III earns very well.
The trap: wage-replacement benefits
Parental allowance, unemployment benefit, sickness benefit and short-time work allowance are based on net pay. Someone in class V has a lower notional net pay and therefore receives less. For parental allowance, the tax class that mainly applied in the months before the birth counts. A switch should therefore be made early, at the latest seven months before maternity protection begins. For unemployment benefit, the employment agency only recognises a switch if it matches the ratio of the two incomes.
Applying for a change
You change your tax class by applying to the tax office, online via the tax administration's portal or on paper. A change is possible several times a year and applies from the following month.
How to proceed
1. Use the part-time calculator to work out the new gross and net pay of the partner who is cutting back.
2. Compare the combinations with the tax class calculator.
3. Check whether parental allowance, unemployment benefit or sickness benefit might be due in the coming months.
4. With unequal incomes and a preference for certainty, choose the factor method; if maximum monthly net pay matters most, choose III/V.
This overview is general information and does not replace tax advice.