landlord refusing to sign N11 form

partner and i are currently living in what we recently learned is an illegal basement unit. we've got a new place lined up for next month and are breaking our 1 year lease early. landlord verbally and through text agreed to end the lease and said he'll have no issue finding new tenants, but is refusing to sign an N11. I want this form signed for my own records and to have a signature indicating we agreed to terminate lease. we want to report the basement for being illegal but also don't want him coming after us for rent if no N11 was signed and technically we're still on the lease, and he loses out on money if he has to stop renting the basement.

any advice on how to proceed ?