Tenant agreed to renew but did not sign the lease, sent payment

[Sean Saadat]

We have a tenant that had a lease expired on the last day of the month in April.

A few weeks back we have inspected the place. LL and T both agreed to extend the lease for another year. We sent them the new lease to sign however, they did not return it even after lease expiration day on April 30th. As a reminder, we emailed them on April 28th requesting sign the lease and send it back as soon as possible, no response.

They have sent in payment for this month, but have not sent their lease back. We sent another text message and email stating "We have not received the lease. Also, no response of email from 04/28/2016. You need to sign and send it back by tomorrow". No response yet.

State California.

I read not to cash the check until they sign the new lease. Is that correct and why?

So what you guys would do if you were in this situation?

Thanks in advance.