The BGH explains that this cannot take place during the security period if the following provision has been agreed, according to which the security is provided for a certain period of time:
"This security - whether as a retention or as a guarantee - serves to secure the rights of the client in the event of defects (§ 634 BGB) (including reimbursement of expenses and advance on costs in the event of self-remedy), any claims for damages by the client (in particular in accordance with §§ 280 ff. BGB) and the client's claims for reimbursement of overpayments under this contract (also with regard to changed and additional services) in the period from acceptance until the limitation period for claims for defects has expired." If the parties to a construction contract also agree that an amount of 5% of the net final invoice amount may be retained as security and that the contractor may redeem this retention by means of a bank guarantee, the customer is not entitled to offset this residual wage claim against a claim from another contract, at least during the agreed security period, after he has retained the amount.
Such a security agreement constitutes a tacit prohibition of set-off agreed in a legal transaction. If the retention has been utilised, claims from other contracts cannot be offset against the client, at least during the agreed security period. Otherwise, the longer existing possibility of offsetting would in fact serve as security for further claims of the client from other contracts, for which there is no justified interest. This is also in the interests of the client, as the due date for the contractor's claim for wages in the amount of the retention is postponed in favour of the client.
