Approaching cosigner about delinquent account

[Marvin Meng]

Hi,

I have a tenant who's habitually late on his rent but usually pays. He's gainfully employed, just not real responsible. Over the last few months he's fallen further behind, incurring late fees. I'd offered him a payment plan where he would pay down the late fees over a few months rent and be caught up. However he has continued to be late, causing more late fees. 

I refuse to allow a rolling/growing total to accrue. (I've been down this road before and learned the hard way.) Yesterday I learned that his October rent check (paid two weeks late) had bounced - so he's now 32 days late. Obviously it's time to serve the five-day notice to quit. And I honestly think this will get his attention for a short while and he'll get caught up. I'm not expecting an eviction to result.

What I'm wondering though is since he has a cosigner, at what point and how do you approach a cosigner? Do any of you have an example letter to a cosigner informing them that their cosignee is delinquent (that you'd be willing to share)? At what point in a delinquency do you approach them and how do you? 

Thank you!