Act quickly: don't miss important tax deadlines in December 2025

Tip 1: Publish 2024 annual financial statements by December 31, 2025 at the latest

Companies in the legal form of a GmbH, AG or GmbH & Co. KG are subject to disclosure obligations. Annual financial statements must be submitted immediately after they have been submitted to the shareholders (but no later than 12 months after the balance sheet date) to the electronic company register to be submitted.

For most companies, the financial year corresponds to the calendar year. The financial statements for 2024 must then be submitted by December 31, 2025 at the latest. This deadline cannot be extended! Anyone who submits late must expect sanctions. It does not matter that tax-advised companies still have until April 30, 2026 to submit their 2024 tax returns (due to the extension of the regular submission deadline).

Tip 2: Apply for loss certificates for capital income by December 15, 2025

The stock market promises both opportunities and risks. Investments in shares or funds can therefore also result in losses. Although these cannot be offset against other income, they can be offset against share gains. No withholding tax is then payable on the share gains. Offsetting only works automatically if all share purchases and sales are processed via the same credit institution.

If the losses were made at a different bank than the profits, a loss certificate is required. The loss certificate must be actively applied for. Without this, it is not possible to offset share losses against share gains in the tax return and the bank will update the loss offsetting pot in 2026.

Note:
Please note the application deadline - you must apply to your bank for the loss certificate by December 15, 2025 at the latest. The same applies here: There is no deadline extension!

Tip 3: Pay attention to the due date of social security contributions

Employers are obliged to settle and pay their employees' wages on time. They must withhold income tax and social security contributions, register them with the tax office or the social security collection agencies and pay them. Deadlines must also be observed here. The total social security contributions are always due on the third-last banking day of the month in which the employment is exercised. For December 2025, these are already due on December 23, 2025 due to the public holidays, weekends and non-bank working days (December 24 and 31). This applies both to social security contributions that you as an employer have to pay to the respective social security collection agencies and to the contributions of those with voluntary statutory insurance. However, the contribution statements for the month of December must be submitted by December 19, 2025.

Tip 4: Submit your voluntary tax return for 2021 by December 31, 2025

Not all employees are obliged to submit a tax return. Even though it always involves a certain amount of effort, in many cases it is worth submitting an income tax return voluntarily. Additional income-related expenses, further special expenses or expenses for household-related services or handyman services often result in a tax refund. You have up to four years to submit the so-called application assessment. This means that a tax return for 2021 can be submitted by December 31, 2025.

Note:
If you are obliged to submit a tax return, e.g. because you received short-time work, sick pay or parental allowance in the past year or because you have other income, the deadline for submitting your tax return for 2024 has already passed and you may be subject to late filing penalties. However, if you are represented for tax purposes, you have until April 30, 2026.

Tip 5: Avoid limitation of outstanding claims

Do you have late payers and outstanding claims from 2022? Then you should check whether an impending limitation period at the end of the year can be postponed with legal dunning proceedings. In day-to-day business, a 3-year limitation period generally applies, which begins at the end of the year in which a claim for action or omission arose. This means that all outstanding claims from 2022 for which no court dunning procedure, lawsuit or acknowledgement of debt has been filed expire on December 31, 2025. If there are claims from so-called continuing obligations, e.g. from tenancy agreements, the limitation period must be checked for each individual claim. If you are unsure how to deal with impending limitation periods, you should seek legal advice.