Batch and expiry are the record
A pesticide that has passed its date is a liability rather than stock, and a complaint about a failed application starts with which batch was supplied. Recording batch and expiry against what you buy and sell is what lets you clear near-dated stock in time, answer a supplier query, and identify affected customers if a batch is recalled. None of it can be reconstructed later.
Litres, packs and dilution
Chemicals sell in several pack sizes at different rates per litre, and farmers compare. Holding pack size on the item means the rate is right and the stock counts bottles rather than an abstract quantity. Dosage and dilution guidance is worth keeping in the item description too, because it is the question asked at the counter more than any other.
Credit through the crop cycle
Like seed, the credit runs to harvest and settles in a concentrated few weeks. What that needs is a limit per farmer set before the season rather than after, ageing so you can see whose balance is stretching beyond one cycle, and a statement at settlement. Because the amounts are individually small and numerous, the ledger has to build itself from the billing or nobody will maintain it.
The number to watch
Stock value within ninety days of expiry. In this trade that figure is the difference between an asset and a write-off, and it is invisible unless expiry is recorded. Reviewing it monthly gives you time to return near-dated stock to the supplier or move it, which is worth considerably more than discovering it after the date has passed.