Here's an interesting glitch in online banking that happened to me and that might happen to you. I use Microsoft Money, which downloads the details of my checking account and credit cards. On the first Monday of each month, my bank charges me a $12.00 service charge for my checking account and then because my balance is over their minimum, they immediately reverse it. So each month, I download from them a transaction that says, "Monthly service fee, $12.00" and then one that says, "Monthly service fee reversal, $12.00." Or at least, I did.
In June, I purchased something off eBay for $12.00 and sent a check to the seller, whom we shall call Myron. As it turns out, that check was dated the first Monday of that month. For some reason, Microsoft Money merged that transaction with that month's monthly service fee. It saw two $12.00 debits the same day and treated them as one.
Ever since then, it's been treating each monthly service fee as if it's a debit to Myron. Each month, I download "Payment to Myron, $12.00" followed immediately by "Monthly service fee reversal, $12.00." Since the balance is correct, I didn't catch it until this week. Suddenly, I noticed that this Myron guy, from whom I bought one silly item in June, had been charging my checking account $12.00 every month since then! I dug up his phone number and called him to accuse him of thievery or worse. I got his voice mail and decided not to leave a message…which was fortunate because a few minutes later, I resorted Microsoft Money to isolate just my $12.00 transactions and that's when I realized my Monthly Service Fees were missing for the same dates as the charges to Myron. After (literally) forty minutes on the phone to the bank, we figured out it wasn't Myron and it wasn't even them. It was Microsoft Money…or maybe it was me not checking its math closely enough.
Anyway, I almost accused an innocent eBay vendor, and there's a lesson to be learned here. Never attribute to larceny that which can be explained by computer error. Or something.