[Date]

[Your name]
[Your address]

[Lessor’s name]
[Lessor’s address]

Dear [Lessor’s name]

Re: Co-tenant break lease for the property at [your address]

I write to inform you that due to reasons beyond my control, I need to vacate the above premises before the end of the current fixed term specified in our residential tenancy agreement. I will be vacating the above premises and return my keys on [date]. 
I acknowledge that by law a fixed-term co-tenancy agreement may not be terminated unilaterally and that until the agreement is validly terminated, all co-tenants’ liability continues. 
Thus I aim to negotiate a mutual termination of the current tenancy agreement. I have the full cooperation of my co-tenants in this matter. I intend to advertise to find a new tenant to take my place on the premises. When all co-tenants agree to a suitable replacement, this person will be referred to you for your approval. 
At that stage, it is anticipated that the remaining and newly-approved co-tenants will sign a new tenancy agreement with you and that all parties to the original agreement sign a statement that that tenancy agreement is terminated.
Please be assured that I will take full responsibility for finding a suitable replacement tenant, and there will be no cost or loss to you concerning this transition. Until a new tenant is found, I will continue to contribute my share of the rent.
Please advise in writing of your response to this proposal.  

Yours sincerely,

[Your signature]  
[Your name]