You have two options in this case. 1) as you have reported the refund of the overcharged expense against the expense that was originally overcharged balances that expense category across multiple reporting periods results in your overall expenses being shown as a negative for the year which isn't truly accurate.
Or 2) reporting the refund as 'other income' which doesn't offset the overcharged expense category, but doesn't skew the reporting of your expense volume for the year.
Either way you have an anomaly to deal with.
In your bookkeeping, you clearly want to address the situation using the first approach, for taxes, the second option may be a more useful approach.
