An inventory system that shows real stock in every location

What an inventory system is for

Most businesses start with a spreadsheet, a stock room somebody knows by heart and the habit of checking before promising anything. That works until the spreadsheet and the shelf disagree. From then on nobody is sure which number to act on, orders get promised against stock that is already gone, and someone spends every week reconciling by hand.

An inventory system fixes that by keeping one record of items, locations, quantities and every event that changed them, then applying an agreed rule for what can be promised to a customer. Reorder alerts, stock valuations and dashboards are all views of that record. If the record is wrong, the views are confidently wrong, which is why we spend most of the effort on the record itself.

This page covers the stock side: items, locations, movements, reservations, adjustments, permissions, counting and reporting. The storefront, the basket and payments belong to e-commerce website development and payment and checkout. Those systems read stock and ask questions of it, but neither should be where stock is defined.

A packaged product is often the cheaper answer, and we will say so. If you sell a few hundred lines from one location under ordinary rules, an off-the-shelf tool will do more on its first day than a custom build can justify. A custom system earns its place when the rules are genuinely yours: allocation by customer, stock committed against contracts, assembled or kitted goods, or a process no product supports without awkward workarounds.

One stock record that every system reads from

Before anything is built, we agree which system holds the stock figure. Stock tends to live in several places at once: the online shop, the point of sale, the accounting package, a warehouse sheet and somebody's memory. If two of them can both change a number, they drift apart, and reconciling them becomes a permanent job nobody was hired to do.

So there is one authoritative record, and everything else has a defined relationship with it. Other systems can read from it and send events that change it, but only one of them holds the number. That single decision removes more future trouble than any feature on the wish list.

Physical, reserved and available are three different numbers

A stock record with one quantity will mislead you. A useful system keeps at least three figures apart, and states in writing how the available figure is calculated.

• Physical stock is what is on the shelf, by location. It changes only when goods actually move, are counted or are written off.
• Reserved stock is physical stock already spoken for: a paid order, a confirmed transfer or a quotation you honour for a fixed period. It is still in the building, but you cannot sell it twice.
• Available stock is what you are prepared to promise, and it is a policy rather than a fact. Usually physical minus reserved, sometimes minus a safety buffer, and sometimes plus goods on a purchase order with a delivery date.
• Incoming and quarantined stock stays outside the available figure until someone decides otherwise. A returned item nobody has inspected is not sellable, whatever the courier tracking says.

Two rules are agreed with you rather than assumed: whether stock may ever go negative, and what happens when two orders arrive for the last unit at the same moment. Both have sensible answers, and neither is ours to choose on your behalf.

How stock moves through the system

The clearest way to plan an inventory system is to follow one item through its life and write down what the system does at each step, who does it and what happens when the step goes wrong. The table does that for a fictional single-warehouse retailer; the roles and rules are illustrations, not a client's process.

Transfers, picks, dispatches and quarantine decisions work the same way: each is recorded as an event with a person, a time and a reason, rather than as an edit to a number. That is what makes the history useful later, because every figure can be explained by the entries that produced it.

When stock has to reach an accounting package, a point of sale or a storefront, we settle four questions first: which system owns the figure, what triggers a change, which way the data flows and who investigates when the two disagree. CRM and integrations explains how we approach those connections, including what we confirm before promising one exists.

Who can change a stock figure

Permissions follow your business process rather than a copied role list. We name, with you, who in your operation may do each of these, and who reviews it afterwards:

• Receive goods and record a problem with a delivery
• Reserve, release or override a reservation
• Move stock between locations and confirm it arrived
• Count a location and submit the result
• Approve an adjustment, especially one that changes stock value
• Decide whether a damaged or returned item can be sold again

The pattern that works in a real warehouse is simple: everyday movements stay quick, and anything that changes value or overrides a rule needs a second person and a stated reason. Every significant change records who made it, when, the figures before and after, and why. That history turns an argument about stock into a five-minute look at the record.

Counting and fixing differences

A count is a process, not a text box. The system holds a recorded quantity, somebody counts the shelf, the difference is calculated, a reviewer accepts or rejects it, and the accepted adjustment is written as its own entry with a reason. Rolling counts by location or by value are usually easier on an operation than closing for a yearly count, and they catch problems while the cause is still recent enough to find.

Reports then come from the same record: movement history by item or location, adjustments by reviewer and reason, ageing stock, items that keep disagreeing with their count and exceptions nobody has closed. We build these into the screens where someone acts on them. Admin dashboards covers the staff-side views in more detail.

Stock across several locations

Once stock sits in more than one place, three questions shape the design. Does a customer buy from a specific location or from the total? Is stock in transit between branches owned by the sender, the receiver or neither? And can one branch see another's figures, or only that stock exists somewhere?

Selling against a total is convenient but risky, because every order is fulfilled from a real place. If a branch can fulfil an order, it needs a way to accept or decline it. Several locations also change how counting works: counts happen per location and the totals are calculated from them.

What to bring to the first conversation

Your item list and how it varies, your locations, the events that change stock today and who handles them, the availability rule you want to promise against, the problems that already cause arguments, and the systems that must connect along with who controls their access. That is enough to size a build honestly, and to tell you if a product would serve you better.