Is this instalment okay? Check it before you pay.
Under a German consumer building contract you are entitled to a 5% security with the first instalment (§ 650m (2) BGB), and instalments before acceptance must not exceed 90% of the price. This checker runs exactly the same engine as BOB’s payment guard — contract sum, change orders, payments so far, new invoice. Applies to projects in Germany.
Updated: § 650m BGB / § 3 MaBV, checked 09/2026
You're entitled to 5% security
With the first progress payment, the contractor must provide security of 5% of the contract sum, as a guarantee or as a retention: €12,000.00.
§ 650m BGB ↗General information, not legal advice. Applies to projects in Germany. If in doubt, ask a consumer advice centre or a construction lawyer.
How this calculator works
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Your case as a mini project
From your inputs the checker builds the same project snapshot the app calculates with: one contract, approved change orders, instalments so far, and the new invoice as a planned payment.
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The same rules as in BOB
BOB’s core guard rules then run on it: the 5% security at the first instalment, the 90% cap before acceptance, invoice above contract sum — with the same hint texts and statute citations as in the app.
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A hint, not a verdict
Each hit names the rule, the amount and the legal reference. BOB gives sourced general hints — not legal advice. When in doubt: consumer advice centre or a specialist lawyer.
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Buying off-plan? Its own path.
Developer purchases follow the German MaBV instalment plan with up to 13 instalments from fixed percentages. That can only be checked against the full plan — in BOB you store it once and every instalment is checked automatically.
General information, not legal advice. Your contract and the individual case prevail; when in doubt, consult a consumer advice centre or a specialist lawyer. German law.
Frequently asked questions
Under a consumer building contract, the contractor must provide security of 5% of the agreed total price with the first instalment (§ 650m (2) BGB) — as a guarantee or a retention. On a €240,000 contract that is €12,000. If change orders raise the price by more than 10%, you are entitled to a further 5% on the increase.
Instalments under a consumer building contract may not exceed 90% of the agreed total including approved change orders (§ 650m (1) BGB). The final 10% or more is paid only after acceptance — your strongest lever for defect remediation.
Single trade contracts follow § 632a BGB: the contractor may claim instalments up to the value of work properly performed. The 5% security and the 90% cap of § 650m BGB apply only to consumer building contracts — typically a whole house from one builder. The checker distinguishes the two cases.
Check first, talk second, pay last: if all invoices together exceed contract sum plus approved change orders, a written change order is usually missing. Request it before paying — verbal agreements on site are the most common source of disputes. In BOB the overrun shows immediately on the item.
Yes. It imports the very function from BOB’s core engine (evaluateGuards) that checks every invoice in the app, and shows the same hint texts with statute citations. What is a snapshot here runs continuously in BOB — on every document, payment and change order.