Article 1076 of the Civil Code, as amended by Law 24-D/2022 of 30 December (the 2023 State Budget), provides in paragraph 1 that "rent may be prepaid, by written agreement, for a period not exceeding two months".
Paragraph 2 of the same article adds that "the parties may secure performance of their respective obligations, by any legally provided means, up to the value corresponding to two months' rent".
Before this amendment there was no explicit legal cap on the deposit, and rent could be prepaid up to three months. In practice it was common to ask for three months' deposit plus the first month prepaid — four months or more due at signing.
Today the combined maximum at both limits is four months' rent (two as deposit plus two prepaid), but the two caps apply separately: a clause demanding three months' deposit is invalid on that point, even if the combined total would otherwise seem reasonable.
Source：https://www.pgdlisboa.pt/leis/lei_mostra_articulado.php?nid=775&tabela=leis
This text is a summary of the law and does not constitute legal advice. For your specific situation, consult a lawyer admitted in Portugal.
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