If you get married, you will automatically be placed in tax class IV at the time of the marriage if

• You are not permanently separated and
• Your place of residence or habitual abode is in Germany.

The registry office will automatically inform the Federal Central Tax Office about the marriage.
Alternatively, you can apply for the tax class combination III and V. You can also choose the tax class combination IV and IV with factor.

Do you not want your employer or the employer of your wife or partner to be informed of the change in marital status? Then you or your wife or partner can apply to your local tax office to have tax class I taken into account. The effect with regard to income tax deduction then corresponds to tax class IV. Alternatively, you can also block your employer from accessing the electronic wage tax deduction features.
If you do this, however, your employer is obliged to tax your wages according to the least favourable tax class VI.

Background information on tax class selection by married couples:
As a rule, the employer only knows the salary of the employee working for them, but not that of the spouse or partner. Consequently, only an employee's wages can be used as the basis for deducting income tax. The wages of both spouses or partners can only be combined after the end of the year as part of the income tax assessment. Only then will the correct annual tax be calculated. It is therefore often unavoidable that too much or too little income tax is withheld during the course of the calendar year. In order to come as close as possible to the annual result, married couples can choose between 2 tax class combinations (IV and IV as a statutory rule and III and V on application) and the factor method.
Which tax bracket combination is the best? This cannot be answered in general terms, but depends on your needs and the circumstances of the individual case.

Combinations IV and IV or III and V:
The tax class combination IVand IV assumes that the spouses earn approximately the same amount. The tax class combination III and V is designed so that the sum of the tax deduction amounts for both spouses roughly corresponds to the joint annual tax if the wife or husband with tax class III earns 60 per cent and the wife or husband with tax class V earns 40 per cent of the sum of both spouses' earned income. As a result, the tax deduction for tax class V is proportionally higher than for tax classes III and IV. This is also due to the fact that in tax class V the basic allowance for the minimum subsistence level is not taken into account, but is doubled in tax class III. If the ratio of actual wages does not correspond to the statutory assumption of 60:40, this can result in back tax payments. For this reason, there is an obligation to submit an income tax return when choosing tax class combinations III and V.

Combination IV and IV with factor:
Instead of the tax class combination III and V, you can choose the factor method in addition to the tax class combination IV and IV. The tax class combination IV/IV in conjunction with the factor to be calculated by the tax office means that the basic tax-free allowance applicable to each spouse or partner is taken into account when deducting income tax by applying tax class IV and the income tax to be withheld is reduced by applying the factor of 0,... (always less than 1) in accordance with the effect of the splitting procedure. The factor is a tax-reducing multiplier that is calculated from the effect of the splitting procedure if the spouses have different wages. Allowances are included in the factor. The factor is automatically provided to the employer as an electronic income tax deduction feature.