Year-end tax preparation is not the right time to reconstruct eleven months of business driving from calendar entries and a fuel receipt pattern.
The IRS standard mileage rate is 67 cents per mile for 2024. For a sole proprietor or independent contractor putting 15,000 business miles on a vehicle annually, that's $10,050 in deductible expenses. The person who documented their mileage consistently gets the deduction. The person who estimated it from memory gets whatever their accountant is comfortable signing off on.
The Record That Survives an Audit
Odometer Start and Odometer End are the fields that make this defensible rather than approximate. The Trip miles field calculates automatically — #{odometer end} - #{odometer start} — so there's no addition error, no rounded estimate. The odometer reading at the start of a client drive is a hard number. So is the reading at the end. Everything follows from those two entries.
The Mileage $ calculation multiplies trip miles by the $ per mile rate. The rate field is set per record, which matters because the IRS standard rate changes annually and some employers use different rates for different vehicle classes or different categories of business travel. Changing the per-mile rate in a single record doesn't affect historical records — each entry carries its own rate at the time of travel.
Client is the field that transforms the database from a personal log into a billing tool. A filter on Client showing all entries for a specific account produces a trip summary for that client's expense reimbursement request without any manual extraction. Sorting by Client and summing Mileage $ produces the annual mileage expense breakdown per client for cost allocation or billing purposes.
The Notes field is for the details that the IRS may ask about: the purpose of the trip, the business nature of the meeting, why a Tuesday morning drive to a location 47 miles away qualifies as business rather than personal. Entered at the time of the trip when it's fresh, not reconstructed from a calendar entry six months later.
Date & Time combined makes the records sort chronologically by default, which is how mileage logs are presented in audits and in most reimbursement claims formats.