What is subletting? Renting your rented home to somebody else while your own lease continues.
In a sublease the original tenant stays on the hook. You remain the landlord's tenant, you still owe the rent, and you become the subtenant's landlord: if they stop paying or damage the place, the landlord looks to you. That is what separates a sublease from an assignment, where the new tenant replaces you on the lease entirely and you walk away, which landlords agree to far less often.
Almost every lease addresses this, and the common wording is that subletting requires the landlord's written consent. Doing it without consent is usually a breach that can end the tenancy, and in some places the landlord may not unreasonably withhold consent, so the answer depends on both the lease and the state.
If you are subletting, put it in writing, screen the subtenant the way a landlord would, collect a deposit, and photograph the condition on the day they move in. You are the one who will be paying for whatever goes wrong.
A worked example
A tenant nine months into a twelve-month lease at $1,600 takes a job elsewhere and sublets for the last three. The landlord consents in writing, the subtenant pays the tenant, and when the subtenant leaves a hole in a door it is the original tenant's deposit that covers it.
See what a lease says about it
Questions people ask
Can my landlord say no to a sublet?
Usually yes, unless the lease or state law says consent may not be unreasonably withheld. Subletting without the consent the lease requires is normally a breach that can end the tenancy.
What is the difference between a sublease and an assignment?
In a sublease you stay liable and become the subtenant's landlord. In an assignment the new tenant takes over your lease and you are released, which landlords agree to less often because it removes them from you as a payer.