Rule #1 for CCs, most loans, and IRS bills: They have interest tacked on DAILY. Thus, if you get a bill, and pay it off in full, you didn't pay it off in full.
Why? Because they printed the bill and it took several days to reach you. Even if you paid it instantly when you received the bill, the debt is higher by the time you got the bill. If you follow the standard practice and waited a bit for paying and/or mailed in a check, then even more time passes.
Example: You owe me $100 today at $1/day interest. I mail you a bill today and you get it in 3 days. By they time you get it on Friday, you owe me $103. If you pay only $100 (even if you pay it on Friday) you still owe me $3. Thus, next month you owe me $3 plus interest on that $3. Rinse and repeat. [/b]You can never pay off a loan by paying a bill in full, unless the bill gives you a specific ADDITIONAL grace[/b].
Solution #1: Pay MORE than you owe. Then I'll refund you the difference. In my example above, if you paid me $105 on that Friday, you'd have a -$2 balance. Then I'd mail you back $2.
Solution #2: Support the politicians who introduced legislation to outlaw this practice this week.