A sale within 10 years of purchase is a taxable "private sale transaction" (privates Veräußerungsgeschäft): the gain is added to your other income for that year and taxed at your personal progressive rate — not a flat capital-gains rate (that flat rate, Abgeltungsteuer, applies only to financial assets like stocks). After more than 10 years of ownership, the sale is entirely tax-free, regardless of gain. §23 Abs. 3 EStG also exempts total annual private-sale gains under €1,000 (Freigrenze), though that rarely matters at real-estate scale.

AfA depreciation claimed while renting the property out is added back into the taxable gain if you sell within the 10-year window — the tax office treats it as a deferral, not a permanent write-off. This is modeled directly: the tool tracks every euro of AfA claimed year to year and recaptures it into the sale-year calculation. See the "why this number" note on the sale proceeds column for the exact formula.

Confirmed: sell after the 10-year mark and you're exempt from BOTH the sale-gain tax and the depreciation recapture — not because the recaptured amount happens to be zero, but because §23 EStG (the provision the whole calculation lives under) simply no longer applies once you're past the holding period, so there's no taxable transaction to add anything back into. This is a genuine difference from the US, where depreciation recapture (IRC §1250) applies regardless of how long you've held the property — German real estate rewards long holds in a way US tax law doesn't.

Sell too many properties too fast and the tax office can reclassify you as a commercial property trader (gewerblicher Grundstückshandel) instead of a private investor — losing §23's 10-year exemption entirely, on every property, not just the recent ones. The commonly-cited rule of thumb is the "Drei-Objekt-Grenze" (three-property line): selling MORE than three properties ("Zählobjekte") within roughly five years of buying each one is treated by the courts as an indicator of commercial trading. It's an indicator, not an automatic trigger either way — courts weigh the overall picture (financing, renovation/development activity, how business-like the pattern looks), and BFH case law has both extended scrutiny past the 5-year mark in unusual cases and declined to apply it just past 5 years with no special circumstances.

The practical takeaway for a buy-and-hold-10-years strategy: a property only counts as a "Zählobjekt" toward the three-property line if it's bought AND sold within roughly 5 years. If you buy one property a year and hold each for 9–10 years before selling (the pattern this tool is built around), none of those sales fall inside that 5-year window — so the count doesn't even start accumulating. Concretely: buy Property 1 in year 0, Property 2 in year 1, Property 3 in year 2, Property 4 in year 3 — and sell each after ~9–10 years of its own ownership (so around years 9–10, 10–11, 11–12, 12–13 respectively). Property 4 doesn't need to wait until "year 12" for some cumulative-count reason; it just needs its OWN roughly-10-year hold, same as the first three. Selling faster than that — flipping several properties within a few years of buying them — is the scenario that actually risks tripping the three-property line, regardless of how many total properties you eventually own.

Linear building depreciation is 3% p.a. for buildings completed after 31 December 2022, and 2% p.a. for buildings completed earlier (a further 2.5% band exists for pre-1925 buildings, not modeled separately here). Applies to the building value only — land is never depreciable, which is why the tool asks for a building-value % split.

Germany's income tax is progressive, not flat: the marginal rate climbs from ~14% to 42% across roughly €12k–€70k of taxable income (2026 bands), then holds at 42% up to ~€278k, above which a 45% top rate ("Reichensteuer") applies. 42% is used as the default because most landlords with meaningful W-2/salary income are already in that bracket — replace it with your own Grenzsteuersatz. A 5.5% solidarity surcharge applies on top only once your income tax itself exceeds roughly €19–20k/year (most taxpayers are now exempt since the 2021 reform); church tax (8–9%) is a further add-on only if you're a registered church member.

Since December 2020, a broker acting for both sides of a residential sale must split the commission equally between buyer and seller (Halbteilungsgrundsatz). Total commissions of ~7.14% (split 3.57%/3.57%) are common, though the exact split and total are negotiable (§653 BGB) and vary regionally.

Real-estate transfer tax is set individually by each of the 16 Bundesländer (Art. 105 Abs. 2a GG), currently ranging from 3.5% (Bavaria, Saxony) to 6.5% (several northern/western states). There's no single federal rate — check your specific state's Grunderwerbsteuergesetz. The tool's closing-cost default is a placeholder blend of transfer tax, notary, and land-registry fees; enter your actual figures for the state and price bracket in question.

Appreciation rate, rent growth, inflation, vacancy rate, and pull-out LTV are modeling assumptions, not legal figures — they reflect typical German market ranges and this tool's own judgment calls, not a law or regulation. Treat every one of them as an editable estimate, and stress-test with your own numbers before relying on the projection.