Most stock problems are not counting problems. They are that the sale, the stock movement and the accounting entry are three separate acts of recording, so they can disagree – and once they disagree, the reconciliation absorbs more time than the original recording ever did.
We build POS and inventory as one transaction. A sale decrements stock and posts to the ledger atomically: either all three happen or none do. That is the same discipline behind the agent wallet engine we built, where a booking and a balance deduction must not be able to diverge, and it is a database property rather than a procedure people follow.
What runs in production today
A POS module operates inside FT-ERP alongside the booking engine and general ledger. Stock and cost tracking at a per-unit level runs in Kingdom Drive, where sixteen cost categories are recorded against individual vehicles.
Where this is the wrong answer
If you run a single retail location with standard products and no unusual workflow, an off-the-shelf POS will be live next week for a fraction of a custom build, and it will be well supported. Custom is justified when the stock movement has to touch something a package cannot model – contracted allotments, per-unit cost attribution, or a ledger you already run.