The client changes the design, adds work or moves the deadlines, and at the final invoice claims that all of it was covered by the lump sum? We help contractors and subcontractors working in Germany to give notice of, price and enforce claims for additional work (Nachträge) under VOB/B and BGB construction contracts, from the first letter on site to litigation. In English, German and Polish, across Germany.
The pattern is usually the same: the work was done because the site had to keep moving, and the argument about the price only starts at the final account.
The client rejects the variation claim because, in its view, the work was covered by the bill of quantities (Leistungsverzeichnis). What decides the matter is the interpretation of the contract, drawings and specification, not who writes “included” first.
A lump-sum contract (Pauschalpreisvertrag) does not close the door to additional payment. Changes instructed by the client are treated differently from mere quantity deviations without any instruction.
The client’s site manager says “do this as well”, with no quote and no signature. Later it matters who gave the instruction, whether that person could act for the client and what was documented.
Missing drawings, late preceding trades (Vorunternehmer), a changed sequence of works. The crew stands idle, costs run, and the client announces a contractual penalty for delay.
The client pays less than the final invoice shows and informs you that this is the final payment (Schlusszahlung). Under a VOB/B contract, short deadlines for a reservation start running from that letter.
The client deducts a percentage from every invoice and does not release the retention (Sicherheitseinbehalt) for years. Yet security is only owed where it was agreed (sec. 17 (1) no. 1 VOB/B).
Whether additional payment is owed, and how much, depends first on what actually happened on site. VOB/B distinguishes several situations, each with its own requirements.
Where a change to the design or another instruction of the client alters the basis of the price of a service provided for in the contract, a new price is to be agreed taking the additional or reduced costs into account, if possible before execution (sec. 2 (5) VOB/B). The right to order design changes rests with the client (sec. 1 (3) VOB/B).
For additional work demanded by the client the contractor is entitled to separate remuneration, but must give the client notice of the claim before starting the work (sec. 2 (6) no. 1 VOB/B). Work that becomes necessary to complete the contractual services must as a rule be carried out on request, unless the contractor’s business is not set up for it (sec. 1 (4) sentence 1 VOB/B).
In a unit-price contract (Einheitspreisvertrag) a deviation of up to 10 % leaves the unit price unchanged. For the excess above 10 % a new price is to be agreed on request (sec. 2 (3) nos. 1 and 2 VOB/B). According to the Federal Court of Justice the actually required costs plus reasonable mark-ups are decisive, unless the parties agreed another method (judgment of 8 August 2019 – VII ZR 34/18, BGHZ 223, 45).
The lump sum remains unchanged as a rule. Changes instructed by the client are nevertheless governed by sec. 2 (4), (5) and (6) VOB/B, also under a lump-sum contract (sec. 2 (7) no. 2 VOB/B). Without an instruction, an adjustment comes into play where the work performed deviates so substantially from what was contracted that holding on to the lump sum is unreasonable (sec. 2 (7) no. 1 sentence 2 VOB/B in conjunction with sec. 313 BGB). The Federal Court of Justice sets no fixed percentage threshold (judgment of 30 June 2011 – VII ZR 13/10, BGHZ 190, 212).
Work performed without an order or in unilateral departure from it is as a rule not paid (sec. 2 (8) no. 1 VOB/B). Payment is owed, however, where the client subsequently approves the work or where it was necessary to perform the contract, corresponded to the client’s presumed intention and was notified without delay (sec. 2 (8) no. 2 VOB/B).
Under a construction contract governed by the BGB alone, the parties first seek agreement and the contractor submits a quote for the additional or reduced remuneration (sec. 650b (1) BGB). If no agreement is reached within 30 days of receipt of the change request, the client may order the change in text form (sec. 650b (2) BGB). The additional remuneration is calculated from the actually required costs plus reasonable mark-ups for overheads, risk and profit, or from an original cost calculation deposited as agreed (Urkalkulation, sec. 650c (1) and (2) BGB).
Sec. 2 (6) no. 1 sentence 2 VOB/B stipulates that the claim for separate remuneration must be notified before the work begins. The provision requires no particular form, but without an e-mail or letter it is hard to prove later that notice was given. Its absence is not always fatal: the Federal Court of Justice has awarded payment even without notice, for instance where both parties assumed from the outset that the work would be paid for, or where the client could not have been in any doubt about it in the circumstances (judgment of 23 May 1996 – VII ZR 245/94, BGHZ 133, 44). Nobody should rely on those exceptions. A notification of concerns about the design (Bedenkenanmeldung, sec. 4 (3) VOB/B) and the notice of remuneration are two different letters with different effects.
A dispute over the amount of a variation claim can outlast the project itself. German law gives the contractor tools that work before any judgment, provided a specific quote was submitted first.
Where the parties have not agreed on the amount, the contractor may include 80 % of the additional remuneration stated in its quote under sec. 650b (1) sentence 2 BGB in interim payments. If less turns out to be owed, the excess is repaid with interest (sec. 650c (3) BGB).
In disputes over the right to order changes and the price adjustment, an interim injunction (einstweilige Verfügung) after the start of construction does not require the urgency to be substantiated (sec. 650d BGB). The Higher Regional Court of Celle applied sec. 650c (3) and sec. 650d BGB to a VOB/B contract as well, but held that vague calculations of the additional remuneration are not enough, and a long delay in filing can rebut the presumption of urgency (judgment of 14 May 2025 – 14 U 238/24, NJW 2026, 236).
The contractor may demand security for unpaid remuneration, including from additional orders, plus 10 % for ancillary claims. After a reasonable deadline expires without result, it may refuse further performance or terminate the contract (sec. 650f (1) and (5) BGB). The contract cannot restrict this right (sec. 650f (7) BGB). Exceptions apply among others to public clients against whom insolvency proceedings are inadmissible, and to consumers under consumer construction and property developer contracts (sec. 650f (6) BGB).
Stopping work merely because the client does not accept the price of the variation can backfire on the contractor. We build lawful pressure through the quote, interim invoices, the demand for security and deadlines.
Under a BGB construction contract the remuneration falls due once the works have been accepted (or acceptance is dispensable under sec. 641 (2) BGB) and a verifiable final invoice (prüffähige Schlussrechnung) has been issued. The invoice is deemed verifiable if the client does not raise substantiated objections within 30 days of receipt (sec. 650g (4) BGB). Under VOB/B the final payment falls due no later than 30 days after receipt of the final invoice, and the client can no longer rely on a lack of verifiability unless it raised that objection with reasons within that period (sec. 16 (3) no. 1 VOB/B).
The final invoice closes the account for the project. The safest course is to include every variation, every price adjustment and all standstill costs, including the disputed ones, and to label them clearly.
Accepting the final payment without reservation excludes further claims if the client informed the contractor in writing of the final payment and pointed out that effect. A written, final refusal of further payments with reference to payments already made has the same effect. Claims raised earlier but still open, such as rejected variations, are also caught unless they are reserved again (sec. 16 (3) nos. 2 to 4 VOB/B).
The reservation (Vorbehalt) must be declared within 28 days of receipt of the notice of final payment. Within a further 28 days a verifiable invoice for the reserved claims must be submitted or, where that is impossible, the reservation must be substantiated in detail, otherwise it lapses (sec. 16 (3) no. 5 VOB/B). The deadlines do not apply to the correction of measurement, arithmetical and transcription errors (sec. 16 (3) no. 6 VOB/B).
Individual VOB/B clauses escape the review applied to standard terms only where VOB/B was incorporated into a contract with a business in the version current at conclusion, as a whole and without changes to its content (sec. 310 (1) sentence 3 BGB). The contract templates of German general contractors frequently modify VOB/B. Whether the exclusion in sec. 16 (3) no. 2 VOB/B operates in a given contract can only be assessed on the whole contract. Until then, act as if it does: a reservation filed within 28 days costs less than a dispute about its absence.
Standstill costs and an extended completion date can only be claimed if the hindrance was documented at the moment it occurred.
A contractor who considers itself hindered in the proper execution of the works must notify the client in writing without delay. Without notice, hindering circumstances are only taken into account if both the fact and its hindering effect were obviously known to the client (sec. 6 (1) VOB/B).
Completion periods are extended to the extent that the hindrance was caused by a circumstance within the client’s sphere of risk (sec. 6 (2) no. 1 (a) VOB/B). Where one party is responsible for the hindering circumstances, the other may claim compensation for the loss it proves (sec. 6 (6) VOB/B). If an interruption lasts longer than three months, either party may terminate the contract in writing (sec. 6 (7) VOB/B).
Concerns about the intended method of execution, materials or components supplied by the client, or the work of other contractors must be communicated to the client in writing without delay, if possible before work starts. The client remains responsible for its specifications, instructions and supplies (sec. 4 (3) VOB/B).
Not every step is needed in every case. The most can be achieved before the additional work is carried out.
Contract, bill of quantities, drawings, minutes and correspondence. We establish what was owed (Bausoll), whether VOB/B was incorporated unchanged and which type of remuneration applies. You know the cost of our work before instructing us.
We draft in German the notice of remuneration, the variation quote with its calculation, notices of hindrance and reservations, so that the requirements and deadlines under VOB/B and the BGB are met.
Interim invoices with 80 % of the quoted additional remuneration, a demand for security under sec. 650f BGB and, where necessary, an application for an interim injunction.
Final invoice including all variations, reservation after the final payment, negotiations with the general contractor or the employer, and representation before courts across Germany.
His doctoral thesis at the European University Viadrina deals with the exclusion of claims for additional work in lump-sum construction contracts (under Polish law, published as a book in Germany in 2021). He handles disputes of construction companies over variations, lump-sum accounts and final invoices.
See the publication →“A German general contractor owed us a six-figure amount. We got a clear plan, tough negotiations — and the money before trial.”
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VOB/B does not make the claims under sec. 2 (5) and (6) dependent on a written instruction. Under a BGB construction contract, the client’s order after the 30-day period requires text form, so an e-mail is sufficient (sec. 650b (2) BGB). Many general contractors’ contracts, however, impose their own form requirements. Whether such a clause is valid, we check against the specific contract. Regardless of that, record every instruction: who, when, what and on the basis of which drawing.
Yes, if the client changed the design, gave another instruction or demanded work not provided for in the contract. The rules of sec. 2 (4), (5) and (6) VOB/B apply under a lump-sum contract as well (sec. 2 (7) no. 2 VOB/B). It is harder where the work grew without any instruction, for example because the quantities turned out larger than assumed. Then an adjustment requires that holding on to the lump sum is unreasonable (sec. 2 (7) no. 1 sentence 2 VOB/B in conjunction with sec. 313 BGB), and the Federal Court of Justice sets no fixed percentage threshold (judgment of 30 June 2011 – VII ZR 13/10).
Not necessarily. The notice under sec. 2 (6) no. 1 sentence 2 VOB/B concerns additional services, and the Federal Court of Justice has awarded payment without it, for instance where both parties assumed from the outset that the work would be paid for or where the client could not have been in any doubt about it (judgment of 23 May 1996 – VII ZR 245/94). For a change to work provided for in the contract (sec. 2 (5) VOB/B) the provision requires no notice. The outcome turns on the evidence from the construction period.
For quantity increases above 10 % in a unit-price contract the Federal Court of Justice applies the actually required costs plus reasonable mark-ups, unless the parties agreed another method (judgment of 8 August 2019 – VII ZR 34/18). The Berlin Court of Appeal (Kammergericht) applies the same approach to sec. 2 (5) and (6) VOB/B while noting that the question is disputed (judgment of 18 July 2025 – 21 U 176/24, NZBau 2026, 47, appeal to the Federal Court of Justice pending). Under a BGB construction contract the method is set out in sec. 650c (1) BGB, and an original cost calculation deposited as agreed is the alternative (sec. 650c (2) BGB). Before you send a quote, check what your contract provides on calculation and mark-ups.
Do not stop the work on your own initiative. Document the instruction and the quote, include 80 % of the quoted additional remuneration in an interim invoice (sec. 650c (3) BGB) and consider a demand for security under sec. 650f BGB. In urgent cases the court may issue an interim injunction without substantiation of urgency (sec. 650d BGB), but the quote must be specific and verifiable (Higher Regional Court of Celle, judgment of 14 May 2025 – 14 U 238/24).
Note the date of receipt and, within 28 days, declare a reservation covering every unpaid item, including variations rejected earlier, preferably in writing with proof of delivery. Within the following 28 days, submit a verifiable invoice for the reserved claims or substantiate the reservation in detail (sec. 16 (3) no. 5 VOB/B). Send us the letter straight away, because the deadlines are short.
Only if security (Sicherheitsleistung) was agreed (sec. 17 (1) no. 1 VOB/B). Where security is retained from payments, VOB/B allows each payment to be reduced by no more than 10 % until the agreed amount of security is reached (sec. 17 (6) no. 1 sentence 1 VOB/B). Unused security for defect claims must be returned after two years unless another date was agreed, and an appropriate part may be retained for claims that have been raised but not yet settled (sec. 17 (8) no. 2 VOB/B).
Yes. The firm is based in Frankfurt (Oder) and represents construction companies before courts throughout Germany. We communicate with you in English, German or Polish, and we draft the letters to the client and to the court in German. You know the cost before instructing us.
Tell us briefly which type of contract it is (VOB/B, lump sum, unit prices), what the client instructed and how far the account has progressed. If you received a notice of final payment, give the date of receipt. You know the cost before instructing us.
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