I want to thank you for writing in with your question, and I'll try my best to answer it here. You can also research this question further on our experts' blog at http://blog.credit.com/credit-score/
As lenders report updates to the credit reporting agencies and your credit report changes, it’s not uncommon for credit scores to fluctuate a few points from month to month. There are a number of reasons why a credit score would drop: a negative item that wasn’t reported in the past, higher balances on credit cards, new account openings, new inquiries — or a combination of these things. It’s easy to speculate what may have caused a score drop but in the end, the only way to truly know what caused a score to drop is to compare the credit reports used to generate the score for each.
I know you mention that nothing else changed but if your score dropped, something in your credit report changed. The free monthly updates from Credit.com’s Credit Report Card only include changes in your score so unless you ordered a full credit report, it’s impossible to know what caused the drop. (You can get your credit reports for free once each year from each of the three credit reporting agencies.) Having said this, there are a few other factors at work here that I think may ease your mind and explain the slight drop.
Paying a credit card balance doesn’t necessarily mean your credit score will reflect your most recent credit card payment. This is because credit card issuers generally report updates to the credit reporting agencies once every 30 days, typically around the time that your monthly statement drops. For this reason, the balance reported in your credit report would show the balance from your most recent credit card statement. And if your most recent statement balance was higher than the previous month’s statement balance (when your score was 812), it would cause your score to drop. So you’d have to stop using your credit card for at least a month before the balance would be updated and reflect a $0 balance in your credit reports.
I sincerely hope this helps answer your question.