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For Facebook Marketplace and cash flippers: haul costing across a whole receipt, a flips log that knows local cash = no fees and FB-shipped = 10% with the $0.80 minimum, mileage with 2026 IRS rates, and a six-tile dashboard.
What's inside
Local cash sales tracked fee-free; FB-shipped fee applied automatically
One thrift receipt allocates across all its items
Profit per flip and average per flip
Mileage deduction with 2026 split-year rates — sourcing AND meetup drives
Tax set-aside tile so January stays boring
15-second parking-lot logging from the Sheets app
Quick-Start PDF + free updates
Questions people ask
Do I need Excel?
No — free Google Sheets works identically. Import steps in the Quick-Start guide.
What happens when platforms change their fees?
Every rate lives in one editable Settings cell — change it once, every formula follows. We also email free updated copies when major rates change.
Phone or computer?
Set up on a computer; logging from the Sheets phone app in a parking lot works great.
What if I break a formula?
hello@thriftmath.com — fresh copy free, forever.
Ready?
Instant download. Five-minute setup. A business you can finally see.