Joint and several liability is a lease term that makes every co-tenant responsible for the full rent and any damages, not only a personal share. When all roommates sign one lease under this clause, you can collect the entire balance owed from any single one of them, regardless of who actually caused the shortfall or how the tenants split costs among themselves.
In practice
Say three roommates sign a single 12-month lease at $2,400 a month, and they have agreed between themselves to pay $800 each. In month five, one roommate loses a job and pays nothing, so the rent lands $800 short. Under a joint and several clause, you are not limited to chasing the one who came up short for $800. You can demand the full $800 from any of the three signers, because each of them signed for the whole $2,400, not for a $800 slice.
The same logic covers damage at move-out. If the move-out walkthrough shows $1,300 in repairs beyond the deposit and one tenant has already skipped town, you can recover the entire $1,300 from the two who remain. They can argue among themselves about fairness later, but that is their problem, not yours. The clause exists so a single missing or broke roommate does not turn into your loss.
Why it matters to a small landlord
For a self-managing landlord renting to roommates, students, or unrelated adults, this one clause is what keeps a group lease collectible. Without it, you are left trying to prove which person owes which dollar, which is nearly impossible once people scatter. The catch is that the clause is only as strong as your screening: if two of three signers have no income or assets, suing them recovers nothing. Run every adult through the same process, not only the lead tenant. See how turnover actually costs out and keep a clean walkthrough record with a move-in and move-out checklist so a damage claim against any signer holds up.
Joint and several liability pairs naturally with a few other terms worth knowing. A guarantor adds a non-resident signer on the hook for the same full balance, which is how you cover a marginal applicant. A sublease can quietly weaken the clause if a roommate hands their room to someone you never approved, so control it in writing. And none of it substitutes for tenant screening on each adult, because a clause you cannot enforce against a broke signer is only words on paper.