How a point of sale manages stock and inventory

Stock management in a POS system follows one rule: every product you can sell carries a quantity, and every sale reduces that quantity by the amount sold. It doesn't replace a physical stock count - it rather automates the deduction and gives you a running view of what should be there. The difference between what the system shows and what's actually on the shelf is where the insight sits.

The process works in three stages:

1. You load products into the POS catalogue with a starting quantity.

2. Each time a staff member sells that product through the POS, the system deducts the quantity sold from the recorded count.

3. You view the remaining quantity and use it to decide on reordering, pricing or what to keep available.

The count updates as each sale goes through, so nobody has to recalculate it between manual counts. Some systems call this perpetual stock tracking.

The system doesn't physically check the shelf. It calculates what should be there based on what was loaded, sold, returned, adjusted and transferred through the software.

A stock record can hold the quantity on hand, a low-stock alert, a reorder point, the cost price, the supplier, the location, separate quantities per variant and a record of manual adjustments. Depending on the system and how it has been set up, a product's stock record may include:

Not every POS system includes every field. Some offer only a basic quantity count, where others support detailed stock records with cost tracking, supplier records and multi-location controls. Which of these fields you get varies by provider and by plan, so check what is included before assuming a field is available.

A sale reduces the recorded quantity automatically when the product is linked to a stock record and the staff member selects the correct product at checkout. Two conditions have to be met:

1. The product is linked to a stock record with a quantity.

2. The staff member selects the correct product at checkout.

If either condition fails, the stock count doesn't update correctly. A sale entered as a general amount (without selecting a specific product) records the revenue and leaves the stock unchanged. A sale entered under the wrong product deducts from the wrong item.

Returns and refunds can work in reverse. If the system is set up to do so, processing a return may add the quantity back to the stock record. Whether that happens automatically or needs a manual step depends on the POS and its settings.

A POS system records transactions, so deliveries, damage, waste, theft, staff use, transfers between locations and any sale made outside the POS have to be entered by hand. It does not observe the physical world. Seven common stock movements happen outside the checkout:

Every event in this table creates a difference between the POS count and the physical count. The more of these events your business has, the more your stock accuracy depends on manual adjustments and regular physical counts.

A stock take means counting what's physically on the shelf and comparing it with the POS count - how often you do it depends on the value and the movement of your stock. High-value or fast-moving items may justify weekly or even daily spot checks. Slower categories may need only a monthly or quarterly full count.

A POS stock count is a calculated estimate based on recorded movements. A physical count is what is actually on the shelf. The two numbers should be close, but they'll rarely match exactly. The difference reveals unrecorded events: damage, theft, receiving errors, incorrect sales entries or adjustments that were never made.

Physical counts serve three purposes:

1. They correct the POS record so future deductions start from an accurate base.

2. They reveal patterns, such as a product that consistently shows a higher loss than expected.

3. They create accountability by showing the difference between what the system expected and what exists.

You prevent stock from going missing by counting your shelves in increments that make sense for your type of business, recording every adjustment, and working out the cause of each variance before you correct the number. The difference between the POS quantity and the physical quantity is called a stock variance or a stock discrepancy. A variance isn't automatically a sign of theft or error. It is a signal to investigate.

Common causes of stock variance:

• A product was sold under a general amount instead of the correct item.

• A delivery was placed on the shelf but not entered into the system.

• Damaged or expired goods were discarded without an adjustment.

• A return was processed physically but not recorded in the system.

• A transfer between locations was completed without updating both records.

• Theft or unrecorded staff use.

• A counting error during the physical check itself.

Always fix the cause before you change the number. If you just fix the number without fixing what went wrong, the same mistake happens again next time.

Stock loss has a tax side. SARS expects you to explain what you bought and sold, so a damaged item that you never recorded in the system creates a gap you can't explain. Always keep the adjustment note with the reason on it, so you can show what happened instead of arguing about it later.

Some POS systems hold a separate quantity for each location, so selling a product at one branch reduces that branch's count and leaves the other alone. A shared catalogue may show the same products across locations, and each location still needs its own quantity.

Stock transfers between locations require a record that removes the quantity from one location and adds it to the other. Without a recorded transfer, one branch shows too much stock and the other shows too little.

Multi-location stock visibility shows you where products are moving fastest, which location is overstocked and where to send stock before you run out. Not every POS system supports multi-location stock management, so check this before you assume it's available.

Some POS systems can notify you when a product's quantity drops below a set threshold. This is called a low-stock alert.

A low-stock alert helps you reorder before running out, rather than discovering the stockout at the moment your customer asks for the item - however, that alert is only useful if the threshold is set at a level that allows enough time for your supplier to deliver new stock.

More advanced systems may support:

• Reorder quantities based on sales velocity.

• Supplier records linked to products.

• Purchase orders created from the POS.

• Receiving workflows that update the count when a delivery arrives.

Not every POS includes these features. Many small businesses manage reordering manually using the POS stock report as a guide rather than as an automated trigger.

The common mistakes are a wrong starting count, sales rung up as general amounts, never counting the shelf, correcting a variance without finding its cause, unrecorded deliveries, and treating the POS count as what is actually there.

Loading products without a starting count. If the initial quantity is wrong or missing, every subsequent deduction calculates from the wrong base.

Selling products as general amounts. Revenue is recorded, but stock is not deducted. The longer this continues, the wider the gap between the POS count and reality.

Never doing a physical count. A POS count that has never been verified against the shelf can drift further from reality with each unrecorded event.

Adjusting the number without investigating the cause. Correcting a discrepancy without understanding it allows the same problem to recur.

Forgetting to record deliveries. New stock placed on the shelf without a POS entry means the system underestimates what is available.

Treating the POS count as truth. The POS count is an estimate based on recorded movements. The physical count is what exists. Trust the shelf, then fix the record.

Ignoring variants. A product with sizes or colours needs separate quantities per variant. Selling a large and deducting a medium leaves both counts wrong.

You keep the count accurate by loading true starting quantities, selecting the correct product on every sale, recording every adjustment and counting the shelf on a schedule.

1. Count the shelf first, then load the starting quantities.

2. Train your staff to select the correct product at every sale. A sale rung up as a general amount records the money and leaves the stock count untouched.

3. Record every adjustment. Damage, waste, staff use, transfers and receiving should all update the POS as well as the shelf.

4. Set low-stock alerts for products that sell consistently, and review the thresholds as your sales patterns change.

5. Count regularly. Use spot checks for high-value or fast-moving items and full counts on a schedule that fits your business.

6. Investigate variances before you correct them. A correction on its own leaves the cause in place.

7. Read your stock count alongside your sales figures. Together they show what sold and what should still be on the shelf.