A tenant can sublet without the landlord's permission, even if the lease says its forbidden. Subletting your apartment for less than 30 days is generally illegal in New York City, especially if you are renting out the entire apartment while you're away.The procedure for subleasing is quite complicated. If your landlord decides to deny your sublet request, the denial must be reasonable. Your landlord cannot unreasonably withhold consent to sublease. Landlords can screen subtenants and deny them based on legally acceptable reasons, but they cannot withhold consent unreasonably. You are entitled to request permission to sublet from the owner, and the owner may not unreasonably refuse such permission. I simply put in my leases. Any subletting is strictly forbidden without the landlords express written permission. A rent controlled tenant who is not occupying an apartment pursuant to an existing lease cannot sublet the apartment without the owner's written consent.