Can you afford to pay the "late" amount? I'd do that and let them credit next quarters bill if it's wrong.

Anyone use them and know by what time payment has to be made on the due date? I realized it's today after asking for an extension. Tried to pay last night on the app but couldn't login until I got to my pc. Making payments for my mom. So there's also a balance fwd charge of 6.90 i'm assuming thats the late fee?