A lease is a synallagmatic contract, which means that the lessor and the tenant have reciprocal commitments and that their signatures on the lease not only demonstrate their agreement of will but also reflect their commitment to legal obligation.
A lease can be signed either at the simple diligence of the lessor and the lessor (i.e. “under private seing” or by in front of a notary (authentic act). When the signature takes place only in the presence of the parties, it proves until proven otherwise, on the other hand when it intervenes in front of a notary, it proves until false registration. But in either case, both the landlord and the tenant must sign the lease agreement. It is required to prepare as many copies of the agreement as there are parties to the lease agreement.
Regarding these signatories in particular, there are a few specific cases that know some specific rules.
On the lessor’s side, when the landlord is married, married, or cohabiting, only one signature on the lease agreement is required. Her spouse’s is optional and not essential.
On the other hand, in the case of an undivided landlord, the signature of the other co-indivisors is required.
On the tenant’s side, the situation of married and married couples is quite similar to that of the spousal landlords. Thus, the signature of only one of the tenant spouses is sufficient to engage them together, as well in the case of PACS. On the other hand, when a couple is in a common-law relationship (neither married nor married), only the spouse who signed the lease will be considered under the law as bound by the lease (obligation) and as the holder of the lease (right).