In theory, the deadline is to the 31st of July of the following year (for people that obligated by law to submit one). However, you can ask for an extension if you are short on time. Using a Steuerberater allows you to have even more time, as they have until February of the year after to do it (eg: a submission in Jul 2024 for the year 2023). Be aware that there is a penalty of 25€ per late month. Important note: employees whose sole income are their salaries are not required by law to submit a tax return. This means that the deadline moves to 4 years in the future. For example, you can do your tax return in Germany for the year 2020 until the last day of 2024. Even more importantly: As an employee, you can claim a tax return for up to 4 years prior the current year. Pretty handy if you forgot to do it those years to maximize return.