Notes from building it.

Every inventory system you can buy assumes you can order more. When quantity is permanently one, the reorder point, the safety stock and the forecast all become meaningless - and what replaces them is not obvious.

The percentage is not the interesting part. What it is charged on is - and most sellers are working from a base that is smaller than the real one.

There are two directions you can build fitment from, and only one starts with something you actually know. The choice decides how defensible your listings are when somebody disputes one.

There are only three ways to stop a part selling twice, two of them are labour, and the honest version of each - including what to do today if you have no tool at all.

eBay's Below Standard threshold is 2% of transactions - and if you sell fewer than 400 in three months, that percentage is measured across a full twelve months of sales.

Overselling is not carelessness. It is what happens when the stock count exists in more than one place and the copies are reconciled on a schedule.