The German corporate income tax return (Körperschaftsteuer), explained and prepared with AI

What corporate income tax is

Körperschaftsteuer is the federal income tax on corporations — the GmbH, UG, AG, SE, KGaA and the cooperative (eG). It is charged at a flat 15 percent of taxable income, with a 5.5 percent solidarity surcharge levied on the tax itself. Partnerships and sole traders do not pay it: they are transparent, and their profit is taxed in the hands of the owners.

The tax base is not simply your commercial profit. You start from the result shown in the HGB income statement and then apply a series of tax adjustments — the reconciliation the German system calls the Überleitungsrechnung — to reach taxable income (zu versteuerndes Einkommen).

From HGB profit to taxable income

The adjustments that turn a commercial result into a tax base.

• Non-deductible expenses are added back — for example, a portion of gifts, certain supervisory-board pay, and the corporate income tax and trade tax themselves.
• Tax-free income, such as qualifying dividends under the participation exemption, is removed.
• Differences in how assets and provisions are measured for tax versus the commercial balance sheet are corrected.
• Loss carry-forwards are applied within the statutory limits (§ 10d EStG), which cap how much of a large profit prior losses can offset.
• The result flows into the Anlage GK of the KSt 1 return and, ultimately, the assessed tax.

How our AI prepares the KSt 1 return

Deadlines, advance payments and assessments

Corporations make quarterly corporate-tax advance payments based on the expected liability, which the software schedules and tracks. The annual return is due after the year end, with extended dates where a tax adviser is involved.

When the assessment notice arrives, the module reconciles it against your own computation to the cent and surfaces the one-month objection deadline (§ 355 AO), so a mistaken assessment can be challenged in time rather than accepted by default.

Where it sits in the platform

• The return builds on the same HGB annual accounts and E-Bilanz the platform produces — one set of figures, not two.
• Trade tax is prepared alongside it, since both start from the commercial result and share several adjustments.
• The corporate-tax cards appear only for legal forms that owe the tax; transparent entities are routed to their own treatment.
• The module is in Beta at 100 euros per month per workspace.

Frequently asked questions

What is the corporate income tax rate in Germany?

A flat 15 percent of taxable income, plus a 5.5 percent solidarity surcharge on the tax. On top of that, a separate trade tax is levied by the municipality, so the combined burden on a corporation is typically around 30 percent depending on the local multiplier.

Why is taxable income different from my HGB profit?

German tax law adds back non-deductible expenses (such as the taxes themselves and part of certain costs), removes tax-free income like qualifying dividends, and corrects measurement differences between the tax and commercial balance sheets. The bridge between the two is the reconciliation the return documents.

Who has to file a KSt return?

Corporations — GmbH, UG, AG, SE, KGaA and cooperatives. Partnerships and sole traders are transparent and file income tax at the owner level instead, so the corporate-tax pages do not appear for them.

Can the software carry my losses forward?

Yes. It keeps a continuous loss carry-forward history per tax type and applies losses within the statutory minimum-taxation limits when it computes the tax base.

What happens after I file?

The tax office issues an assessment. The module reconciles that assessment against your figures to the cent and tracks the objection deadline, so a discrepancy can be identified and appealed within the statutory period.