Six months from the day the property was handed over. Not six months from the day you found the defect, which is what catches people. It is the shortest and harshest period in Spanish property law. A separate route, setting the contract aside for mistake or deceit, has four years counted from completion of the contract, and is a different claim with different requirements.
Where this comes from: art. 1490 Codigo Civil, with art. 1484, BOE consolidated text, read 2026-09-10; art. 1301 Codigo Civil, BOE consolidated text, read 2026-09-10.