As you check each entry to be sure the numbers are correct, highlight the Excel cell in a different color, and make a check mark on the printout of whatever you are comparing it to. At the end you may have an unchecked or unhighlighted entry that will be the culprit.

Also, make sure that everything to be subtracted was subtracted and not added by mistake. Is there a "minus" sign or parenthesis preceeding every entry that is to be subtracted?

The value of the difference between the actual vs. expected balance may be the amount of some regular payment that you forgot to enter.

And of course, as V suggested, make sure the ranges specified in your formulas are correct.