Free lesson · 9 minute read · Reselling Foundations
Create a Transaction Record That You Can Trust Later
Track enough detail that profit, returns, and taxes do not depend on memory.
Your goal
Know the minimum data to record for purchases, individual units, and sales.
When to use
Use from the very first purchase, even if you are only selling a few items per month.
Why this matters
Memory breaks as volume grows. Clean records let you calculate profit, investigate refunds, prepare taxes, and understand what inventory is actually working.
The lesson
A transaction record should answer three questions months later: what exactly did I buy, what did it really cost, and what happened to it?
At purchase time, record date, source/supplier, product identity, quantity, currency, purchase price, taxes/fees/shipping, and total landed cost where relevant. If you bought multiple items together, record enough detail to allocate cost across them.
At unit level, track the exact physical item when condition or identity matters. Used electronics are a perfect example. Two MacBooks with the same model can have different serial numbers, battery health, cosmetic wear, purchase cost, repairs, and warranty. That means a product-level record and an individual-unit record serve different purposes.
At sale time, record actual sale price, buyer/payment status, date, fees, shipping, and which exact inventory unit left the business. Capture cost basis at that time so later edits to inventory do not rewrite history.
Keep supporting evidence: photos, receipts, supplier invoices, messages, shipping documentation, and serial identifiers where appropriate. You do not need enterprise accounting software on day one. A spreadsheet can work. The important thing is consistency.
The value becomes obvious during problems. If a buyer returns one of three identical laptops, you need to know which serial came back, what condition it had before sale, what you paid, and whether it should be restocked.
Records also improve buying decisions. Once you know average profit, days to sell, defect rate, and source by category, you can stop relying on anecdotes.
Worked example
You buy three iPads in one $1,200 bundle. Instead of recording '3 iPads — $1,200,' allocate a reasonable cost basis per unit using negotiated values or relative resale values. When one sells for $600 and another needs a repair, you can still understand the economics of each unit.
Practical checklist
- Purchase date/source
- Product and exact unit identity
- Landed cost
- Condition/battery/serial
- Sale date and price
- Payment status
- COGS
- Supporting evidence
Common mistakes
- Tracking only sale price
- Lumping multiple units into one undifferentiated record
- Editing old cost values after the sale
- Keeping important evidence only in the camera roll
Key takeaways
- Records create memory for the business
- Used goods often need unit-level tracking
- Good records make problems easier to solve
Put this into practice
Create a one-page transaction record template and enter your last five purchases and sales.
Before you finish
You could identify the exact cost and history of any current item without relying on memory.
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