How Does Marriage Affect Taxes in Germany for Expats?

In most cases getting married is relevant for tax purposes. Married couples can file a joint income tax return (they can also opt to file separate returns and they can exercise this option from year to year). If one spouse is on a higher level of income than the other spouse it is beneficial to file a joint tax return. This is because the partner with the higher income may be able to use up tax credits which the other partner is unable to use up as his / her income is not high enough. You can enjoy the full effect of this mechanism even if you are only married for one day during the tax year.
Your employer will apply your tax credits depending on which Tax Class (Steuerklasse) you choose.

The Tax Classes for married couples are:
Tax Class 3: Ideal for one income couples and couples with two significantly different levels of income. The partner in Tax Class 3 can enjoy the full tax credit of both partners. If one partner selects Tax Class 3, the other partner will automatically be allocated Tax Class 5. Tax Class 5 is used by the partner with no or rather low income as it comes with no tax credits.

Tax Class 4: Ideal for couples with relatively similar levels of income. Tax credits are split equally so both partners can enjoy them fully.

Tax Class 5: This Tax Class corresponds with Tax Class 3 (see above) and does not come with any tax credits. Typically used by the partner with no or rather low income.

These tax classes are relevant for your employer so they can withhold the appropriate amount of tax from your salary month by month.

Should you have opted for the wrong tax class and your employer withheld too much or too little tax from your salary throughout the year – no problem. This will be adjusted through your year end tax return and you will get the difference refunded in full or you may have to pay back a shortfall. In the end you will not lose anything by being in the wrong tax class during the year.

All of the above applies equally for same sex marriages and registered partnerships.