Simply replace the unfilled areas such as "" and "[date]" with your information.
Dear [accounting rep or CFO],
Attached please find my monthly expense report for [month and year], as well as copies of all receipts associated with these expenses. If prior approval for any expense was required, this documentation is included as well.
Please process my expense report with the next batch of invoice payments. If you have any questions about any item listed on the report, or find that any documentation regarding these expenses is missing, please let me know and I will get that information to you.
Thank you for your attention to this matter.