One of you is moving out in six weeks, you have found someone to take the room, and everyone involved thinks the problem is solved.
On paper, nothing has happened yet. The lease still names the person who is leaving, they are still liable under it, and so is everyone else who signed. Handing over a key and a Venmo request does not change who the landlord can pursue if the rent is short in March.
The gap between someone physically leaving and someone being legally replaced is where this goes wrong. Replacing a roommate mid-lease in Boston works one of three ways: a lease amendment, a new lease, or an assignment. All three run through the landlord.
Is a roommate still liable after they move out?
Usually yes. Under a standard shared lease, everyone who signed is on the hook for the whole rent, not a share of it, so moving out does not remove a roommate from the lease. We cover how that works in applying for a Boston apartment with roommates.
The consequence for a swap is widely missed. The departing roommate's obligation does not end when they move out. It ends when the paperwork says it ends. Until then, a landlord chasing unpaid rent can pursue them, and the departing roommate may be able to recover that money from the roommates who stayed.
That cuts both ways, and it is why the person leaving usually wants this done properly even more than the people staying do.
The three ways a swap actually happens
| Route | What it is | What the landlord does | Who is liable afterward |
|---|---|---|---|
| Lease amendment | The new person is added to the existing lease and the departing one is released | Approves, screens, signs an amendment | The new group. The departing tenant is released in writing |
| New lease | The whole household signs a fresh lease | Approves and issues a new document | Whoever signs the new lease |
| Assignment | The departing tenant transfers their interest to the new person | Consents to the assignment | Depends on the wording. Without a written release, the original tenant may remain liable |
The common thread is that the landlord is involved in all three. Under most Boston leases, there is no version of this that works by agreement between roommates alone.
Route 1: the landlord adds them to the existing lease
Adding the new person to the existing lease by amendment is usually the cleanest route. The landlord screens the incoming person the same way they would any applicant, and if approved, an amendment adds them and releases the person leaving.
The thing to insist on is the release in writing. An amendment that adds the new tenant but says nothing about the old one can leave the departing roommate still named, still liable, and very unhappy about it six months later. If you are the one leaving, do not sign anything that adds someone without also releasing you.
Route 2: everybody signs a new lease
Some landlords will not amend and will simply issue a new lease to the new household. This is clean in a different way, because the old lease ends and a new one begins with the current occupants.
Two things to watch. The new lease is a new negotiation, so the rent and the terms can change, and in practice the term often resets to a full year from the new start date. If you are midway through a lease you liked, check what you are being asked to sign rather than assuming it is the same document with a different name on it.
Route 3: an assignment
An assignment transfers the departing tenant's interest in the lease to the incoming person. It is a real mechanism, and people often mix it up with subletting.
The critical detail with an assignment is the written release of the original tenant. An assignment with the landlord's consent and a written release does what everyone wants. An assignment without that release can leave the original tenant liable for a tenancy they no longer live in or control, which is the worst outcome available here.
Is replacing a roommate the same as subletting?
No. A replacement removes the original tenant from the arrangement with the landlord's agreement, while a sublet leaves the original tenant on the lease.
In a sublet, the original tenant stays on the lease and becomes the subtenant's landlord. The original tenant remains fully responsible to the actual landlord. It is designed for temporary absences.
In a replacement, the original tenant is removed from the arrangement entirely, with the landlord's agreement. It is designed for permanent departures.
Using a sublet to handle a permanent move-out is a common mistake. It leaves the departing person responsible indefinitely for an apartment they do not live in. If you are leaving for good, you want a replacement, not a sublet.
The sublet rules themselves are in the rules for subletting Boston apartments.
What happens to the security deposit when a roommate is replaced?
In practice, the incoming roommate usually pays the outgoing roommate their share of the deposit directly, and the landlord's deposit stays untouched until everyone eventually leaves. This is the part that causes arguments, so it helps to separate two different questions.
Between the landlord and the tenants, the security deposit is governed by Massachusetts law and the landlord generally holds one deposit for the unit until the tenancy ends. A roommate leaving mid-lease does not usually trigger a return of their portion, because the tenancy has not ended. A new lease is the exception. The old tenancy ends, so ask the landlord in writing whether the deposit will be returned or carried over to the new lease.
Between the roommates, how the departing person gets their share back is not something the deposit statute covers. It is a private matter between you. At the end of the tenancy the landlord generally returns the deposit to the tenants on the lease, so settle the departing roommate's share before they come off it.
The buyout happens at handover. Agree on that number in writing before the keys move.
Does your landlord have to agree?
No general rule says a landlord must approve a replacement roommate, and many leases give the landlord broad discretion over who joins a tenancy. Some will approve a qualified replacement readily because a filled unit is better than a vacancy. Others will not engage at all mid-term.
Because of that, ask early rather than presenting a finished plan. A landlord who feels consulted tends to be more cooperative than one who is informed.
How long does it take to replace a roommate?
A reasonable planning assumption is six to eight weeks from "we have found someone" to "the paperwork is signed," which is longer than most people expect. The incoming person usually has to apply and be screened like any other applicant, and documents, references and signatures all take time that the rent does not wait for.
No amount of searching changes how long your landlord takes to approve a replacement, so find a candidate who can pass screening before you set a move-out date. If you are the one leaving, start your own search early too. You can browse apartments across Boston on Spot Easy, where every agent is verified before a listing goes live.
If the person leaving simply goes, stops responding, and will not sign anything, that is a different problem and a genuinely messy one. Get advice specific to your lease before you act, rather than assuming their departure solved anything.
FAQ
Is my roommate still responsible after they move out? Usually yes, until a written release or a new lease says otherwise. Physically leaving does not end a lease obligation.
Can we just swap names on the lease ourselves? Usually no. Under most Boston leases, all three routes need the landlord's involvement, and an agreement between roommates alone does not change the lease.
Should we do a sublet instead, since it is faster? Not for a permanent departure. A sublet keeps the original tenant responsible, which is precisely what someone moving out for good does not want.