Your tax office will reduce the relief by one twelfth for each full calendar month in which the conditions were not met.
Background:
In 2021, the Federal Fiscal Court ruled that jointly assessed spouses can also claim the tax relief for single parents in the year of marriage on a pro rata basis. Condition: The spouses did not live in a household with another adult before the marriage (BFH ruling of 28.10.2021, III R 57/20).
Furthermore, the Federal Fiscal Court ruled that in the year of separation, the relief is to be granted on a pro rata basis for the months after the separation if individual assessment is chosen and no other adult lives in the household (BFH ruling of 28.10.2021, III R 17/20).
According to the Federal Ministry of Finance, both rulings are to be applied immediately (BMF letter of 23.11.2022, BStBl 2022 I p. 1634).