So here's what's going on from the tenant's POV: he's been paying a premium to rent a unit with central A/C all winter long (Did you also raise the rent last year in a way that could be construed to be related to the service calls?).

If you have not already, there are three ways to get an extension: E-file extension for free e-file their extension form for free.By paying an estimate of their income tax due and indicate that the payment is for an extension using Direct Pay, the Electronic Federal Tax Payment System (EFTPS), or a credit or debit card.

I never suggest credit cards, but in this case I think it has value.

Perhaps you hit your daily limit.Either way, as I see it, Charlie had already saved your @ss, so you owe him at least a $50 gift card to his favorite restaurant.

If the taxpayer raises it, then you might be time barred. 

You're going to raise rents and/or lower expenses and make it cash flow2.

This approach should raise flags.

You can't just raise rents at will and for fun.

You do not need to sign a new lease every time you raise the rent.

Sadly the most important thing to credit is time, but given a year it’s theoretically possible to raise your credit score up by 200 points.