Retention money (kaucja gwarancyjna)
Retention money is the part of the payment the client holds back as security for fixing defects during the warranty and statutory defect liability period. The amount, the way it is withheld and the release dates come from the contract, not from statute.
The mechanism is simple. An agreed part of every interim invoice is deducted and stays with the client. One portion usually comes back after final acceptance, the rest once the warranty or defect liability period ends. Instead of cash, contracts often allow a bank or insurance guarantee, which keeps the money in the business at the cost of a fee.
A general contractor stands on both sides of this chain: the client holds retention on it, and it holds retention on its subcontractors. The dates in the two contracts rarely line up, so a firm can release a subcontractor's retention long before recovering its own. Separately, the Polish Civil Code makes the investor jointly liable for paying subcontractors, and a retention clause does not remove that.
The biggest trap is a release date nobody remembers. Retention has no invoice of its own and no reminder in the ERP. It is an amount deducted three years ago under a contract nobody reads any more. Subcontractors chase their own money, but retention held by clients can sit there untouched.
You recognise the problem when nobody can say offhand how much money is held by your clients and how much you hold for others, and the retention register is a spreadsheet maintained by one person.