When you are in the section for your Schedule "C", enter an additional line item of "General Income" (Not Reported on 1099-MISC or 1099-NEC) and list the description as reimbursed travel expenses. This will be enough of an explanation for the IRS.
Business Income > Business Income and Expenses > Business Income > "Any General Business Income" - and here enter the description and the amount you are trying to reduce the expense by.
