Methodology

This page says in full what the calculators do and where every number comes from. If you cannot follow a result, that is our failure — please tell us.

Structure and numbers are kept apart

The shape of the rules lives in the code; the numbers live in a versioned file. Statutes rarely change shape but change their amounts every year. That is what makes the annual update a change to exactly one file — and what lets the tests assert properties of the rules that hold across years.

Sources

The calculators model these provisions:

• Bundeselterngeld- und Elternzeitgesetz (BEEG)
• Sections 2c, 2e, 2f BEEG
• Section 32a EStG (Einkommensteuertarif), Fassung ab Veranlagungszeitraum 2026
• Mutterschutzgesetz (MuSchG)
• Section 24i SGB V, Section 20 MuSchG

Annual update

The parameters are reviewed at the turn of the year, and again whenever something changes mid-year. The procedure is documented in CALCULATIONS.md in the source and amounts to a new parameter file and one line in a registry.

Parameters for 2026

Verification status of each value

Values stated directly in a statute were checked against the statute text during the build. Values from ordinances and ministerial announcements — contribution rates, contribution ceilings, the average supplementary rate — are still outstanding. They are listed here in full so that nobody mistakes them for verified:

• Freigrenze (Einzelveranlagung) — Section 3 Abs. 3 SolZG 1995, Fassung 2026
• Beitragssatz Rentenversicherung — Section 158 SGB VI
• Beitragsbemessungsgrenze Rentenversicherung — Sozialversicherungsrechengroessenverordnung 2026 (SVBezGrV 2026)
• Ermaessigter Beitragssatz Krankenversicherung — Section 243 SGB V
• Durchschnittlicher Zusatzbeitrag — Bekanntmachung des BMG nach Section 242a SGB V fuer 2026
• Beitragssatz Pflegeversicherung — Section 55 Abs. 1 SGB XI
• Beitragssatz Arbeitslosenversicherung — Section 341 Abs. 2 SGB III
• Beitragsbemessungsgrenze Kranken- und Pflegeversicherung — Sozialversicherungsrechengroessenverordnung 2026 (SVBezGrV 2026)
• Mutterschaftsgeld des Bundesamts fuer Soziale Sicherung — Section 19 Abs. 2 MuSchG i.V.m. der Praxis des Bundesamts fuer Soziale Sicherung

What these calculators cannot do

• Profit income from self-employment (§ 2d BEEG) is not modelled. The calculators assume income from employment.
• Excluded months in the assessment period (§ 2b BEEG) — such as months with Mutterschaftsgeld for an older child — are not modelled.
• The flat-rate wage tax follows the structure of the official calculation plan but is not a byte-exact reimplementation. In tax class V the result may differ slightly.
• The partnership bonus (§ 4b BEEG) and Kindergeld are planned for a later version.
• Special cases such as several employers, employment abroad, or employment bans outside the protection periods are not modelled.