Over a year ago three of us moved into a house. We all signed a year lease. The landlord accepts 3 separate checks from us as we pay different amounts and wrote on the lease how much deposit money we each gave.
Once the year lease ended, we went to month-to-month. Verbally we all agreed to stay in the unit until the end of December. 3 weeks ago one roommate told the rest of us that he was moving out at the end of September. While we aren't happy, we know that a verbal agreement between the 3 of us to stay until December means nothing.
The thing is, he has not informed the landlord of this. He plans to move at the end of the month, and while we have tried to find a third, the search hasn't been working.
My question is - is he still liable for rent because he hasn't given notice? I know that even if he leaves, the full rent still needs to be paid by the two of us, but can the landlord take his security deposit and apply it to another month of rent since he did not give notice and is still on the lease?
I don't want to do his job for him and tell the landlord of his plans. If I call the landlord about the situation, is that basically giving his notice for him or does he have to submit a written notice to vacate?
Thanks in advance for any advice!

