Controlling Parts Stock with Batch Stock Cards

Parts & Inventory By Automan Team Published Updated 3 min read

The same LCD model can carry different costs because it was bought at different times from different suppliers. Merge everything into one number and profit can look better — or worse — than reality.

This article explains what a batch stock card is — “batch” here simply means one purchase, one delivery — why it’s more honest than a single stock figure, and what it looks like day to day.

One product, many batches

Picture it (as an illustration): the shop buys the same LCD model three times — last month from supplier A, two weeks ago from supplier B at a cheaper price, yesterday from supplier A again after a price rise. On the shelf, all three look identical. In the books, they are three batches, each with its own cost.

A batch stock card records every arrival as its own line: which purchase it came from, how many arrived, how many are used, how many remain, and at what cost. Three important questions get answered without manual math:

  • Where did this item come from? — crucial when claiming supplier warranty.
  • How much stock actually remains? — per batch, not a lumped guess.
  • What did the goods we used actually cost? — the basis of honest profit.

Why not just one average number?

Simple systems store one figure: “LCD X: 7 left.” Practical — but three pieces of information vanish: the goods’ origin, the stock’s age, and the cost of each unit consumed.

With batches, when a part is used for a repair or sold, the system knows which batch it came from and what it cost — cost-of-goods (known as COGS) runs automatically by whichever method the shop uses, for instance FIFO: the batch that arrived first is consumed first. You don’t need the jargon to get the benefit; what matters is that profit is computed from real cost.

A quick numeric illustration (hypothetical): first batch 8 pcs @ $10, second batch 10 pcs @ $12. Sell 10 pcs under FIFO → recognized cost = 8 × 10 + 2 × 12 = $104, not 10 × a guessed price. The average method computes differently — either is valid as long as it’s applied consistently.

A stock card showing inbound movements from purchases and outbound to repairs and sales, each pointing at its source transaction
The stock card: every movement points at its source transaction — the balance is always accountable. (App UI shown in Indonesian.)

Shipping is part of cost too

Parts bought online arrive with a shipping fee. If shipping isn’t allocated to the goods, cost is recorded cheaper than reality — and profit looks fatter than it is. Good purchase recording offers a way to spread shipping across the purchase’s items, so per-unit cost already includes the price of getting it to your door.

From purchase to report: one straight line

Batch-level control isn’t extra work when the flow is connected:

  1. The purchase is recorded → a new batch forms with its quantity and cost (shipping included).
  2. A repair consumes a part → the work record deducts the batch; the consumed cost lands on that repair’s invoice.
  3. A part is sold → the same: stock drops from the batch, cost rides along with the transaction.
  4. Reports → profit is computed from selling price minus the batch cost actually consumed — not from assumptions.

Line 4 is why any of this is worth doing: owner reports are only as honest as the stock data underneath them.

Where to start

No need to fix everything at once. The realistic order: record purchases properly first (supplier, quantity received, price, shipping), let batches form, then bring discipline to parts usage through repairs and sales. The stock cards will follow — and from then on, “how much money do we have in this item?” is answered by the system, not estimated. More in spare parts inventory.