Knowing how much it truly costs to sell each product is one of the clearest ways to improve business profit margins. Many Australian business owners can see sales rising, yet still feel cash is tight or profits are underwhelming. Often, the missing piece is a reliable Cost of Goods Sold, or COGS, calculation.

COGS helps you identify the direct cost of the stock you have sold during a period. When it is calculated consistently, it gives you a more useful view of gross profit, pricing, purchasing, stock control and the products that are actually contributing to the business.

What Cost of Goods Sold means for an Australian business

Cost of Goods Sold is the cost of inventory that has been sold to customers in a particular reporting period. It is not simply the total amount spent with suppliers during that period.

For a retailer, COGS will generally relate to products bought for resale. For a manufacturer, it may also include materials, components and direct production costs associated with goods produced for sale. For hospitality businesses, it commonly includes food and beverage ingredients. For a trade business that sells materials as part of jobs, it may include the materials used or supplied to customers.

Australian tax law refers to “trading stock”, which broadly includes things produced, manufactured or acquired and held for manufacture, sale or exchange in the ordinary course of a business. It can include finished products, raw materials and partly completed goods.

The key point is that COGS relates to goods that have left your business through sales or use. Stock still sitting on shelves, in storage, in the workshop or in transit at the end of the period is generally not part of that period’s COGS calculation.

This distinction matters because a business can make substantial purchases without having sold those items yet. Recording all purchases as an immediate cost can make one month appear unprofitable and the next month look unusually profitable, even though neither result reflects the underlying trading performance.

The basic COGS formula

The standard calculation is:

Opening inventory + purchases and direct costs − closing inventory = Cost of Goods Sold

Each component needs to be accurate and treated consistently.

Opening inventory

Opening inventory is the value of stock on hand at the beginning of the reporting period. For an established business, this should normally agree with the previous period’s closing inventory figure.

Examples may include:

  • Products held for resale

  • Raw materials

  • Packaging that forms part of the product sold

  • Work in progress

  • Finished goods ready for sale

  • Components used to manufacture saleable goods

If your opening figure is inaccurate, every gross-profit calculation that follows may also be unreliable. That is why a well-documented closing stocktake is so important at the end of each financial year and, ideally, at regular intervals throughout the year.

Purchases and direct costs

Purchases are the goods acquired for resale or for use in making products for sale. Depending on the nature of the business and the reporting purpose, the calculation may also include direct costs needed to bring stock into a saleable condition.

These can include:

  • Supplier invoices for stock

  • Freight or delivery costs to bring stock into the business

  • Customs duty and import-related costs where relevant

  • Direct manufacturing materials

  • Direct labour involved in producing goods

  • Product-specific packaging

  • Other costs directly connected with preparing inventory for sale

Supplier returns, rebates, credits and discounts should also be considered. If a supplier has issued a credit for damaged stock or returned goods, that should not remain in the purchase cost base.

Not every business expense belongs in COGS. Rent, accounting fees, advertising, office software, bank fees, general administration wages and insurance may affect net profit, but they are usually operating expenses rather than direct costs of the goods sold.

Closing inventory

Closing inventory is the value of stock still on hand at the end of the period. It reduces COGS because those goods have not yet been sold.

For income tax purposes, businesses that account for trading stock are generally required to compare the value of trading stock held at the start and end of the income year. The law permits each item of closing trading stock to be valued using cost, market selling value or replacement value. A lower value may also be available where an item is obsolete or special circumstances make a lower reasonable value appropriate.

This is an area where consistency and evidence matter. A lower stock value should not be used simply because it produces a better tax outcome. There needs to be a genuine commercial basis, such as damaged, outdated, discontinued, slow-moving or unsaleable goods.

Why COGS is central to gross profit and pricing

COGS is used to calculate gross profit:

Sales revenue − Cost of Goods Sold = Gross profit

Gross profit is the amount left from sales after accounting for the direct cost of the goods sold. It must then cover operating expenses, finance costs, tax obligations and, ultimately, profit for the owner or business.

A business can have strong turnover and still struggle if its gross profit margin is too low. This can happen when supplier prices rise, discounts are given too freely, wastage increases or selling prices have not kept pace with the true cost of supplying the product.

Regular COGS reporting can help you answer practical questions such as:

  • Which products produce the strongest gross profit?

  • Are supplier price rises being passed on appropriately?

  • Is a popular product actually profitable after freight, packaging and wastage?

  • Are promotions increasing sales but reducing margin too far?

  • Are stock losses or discrepancies affecting results?

  • Is excess inventory tying up cash without generating enough return?

For example, a small online retailer may see sales increase after introducing discounted bundles. However, once the business includes product cost, inbound freight, packaging and higher rates of returns, the bundles may deliver a much lower gross margin than expected. The sales volume looks positive, but the COGS analysis shows that the promotion needs to be repriced or redesigned.

COGS does not make pricing decisions for you, but it provides a much stronger foundation for making them.

What to include, and what to keep separate

Accurate classification is one of the most important parts of a useful COGS system. The right treatment can depend on your industry, your accounting method and the reason you are preparing the report, whether for management, finance, tax or lending purposes.

As a practical starting point, direct stock-related costs may be included in COGS where they are clearly connected with acquiring, manufacturing or preparing the goods for sale.

Costs commonly connected with COGS

Depending on the business, these may include:

  • Goods purchased for resale

  • Raw materials and components

  • Direct production costs

  • Freight-in and delivery charges from suppliers

  • Import costs directly related to stock acquisition

  • Packaging supplied with the product

  • Costs of converting raw materials into finished goods

  • Direct labour used in manufacturing or production

  • Stock write-downs supported by a genuine commercial basis

  • Inventory losses, wastage or shrinkage that have been identified and recorded

Costs that are usually operating expenses instead

These are generally considered separately from COGS:

  • Advertising and marketing

  • Website hosting and general software subscriptions

  • Rent for a shop, office or warehouse

  • General administration wages

  • Merchant fees and bank charges

  • Professional fees

  • Business insurance

  • Utilities

  • General vehicle expenses

  • Interest on business loans

  • Depreciation of general business equipment

The distinction is important because a business owner may otherwise misunderstand where a margin problem is occurring. If gross margin is healthy but net profit is weak, the issue may be overheads rather than the cost of stock. If gross margin is weak, the focus may need to be supplier pricing, product pricing, purchasing practices or stock control.

GST, stock records and the importance of clean data

For many GST-registered businesses, inventory and direct purchase costs are commonly tracked on a GST-exclusive basis where the business is entitled to input tax credits. This aligns with the income tax trading stock rules, which require eligible input tax credits to be disregarded when working out the relevant value of trading stock.

However, GST treatment can become more complicated where purchases are not fully creditable, are partly private, relate to input-taxed activities or involve special arrangements. It is sensible to obtain advice before assuming every stock-related amount should be recorded the same way.

Good COGS reporting depends on sound record keeping. The ATO expects businesses to keep records that explain income, expenses and transactions relevant to their tax affairs. For inventory-based businesses, that usually means maintaining a clear audit trail between supplier documents, purchase orders, receiving records, sales records, inventory systems and stocktake results.

Useful records include:

  • Supplier invoices and tax invoices

  • Purchase orders and delivery dockets

  • Inventory reports from your point-of-sale or accounting system

  • Records of stock received, returned, damaged or written off

  • Stocktake count sheets

  • Details of supplier rebates and credits

  • Product costings for manufactured or assembled goods

  • Notes explaining significant adjustments or valuation changes

A bookkeeping system that combines sales data with inventory data can make reporting far more timely. But software is only as reliable as the information entered into it. If goods are received but not recorded, if stock is taken for private use without adjustment, or if returns are processed inconsistently, reported COGS can quickly become misleading.

A practical process for calculating COGS

A disciplined process does not need to be overly complex. The aim is to produce a number you can trust and compare from one period to the next.

Start with a regular reporting period

Monthly reporting is often useful for businesses with frequent sales, changing supplier prices or high volumes of stock. Some smaller businesses may begin with quarterly reporting, but waiting until EOFY can make it harder to identify pricing and stock issues early.

Use the same reporting period consistently so you can compare results over time.

Reconcile opening stock

Confirm that the opening inventory figure agrees with the prior period’s closing stock figure. If it does not, investigate the difference rather than simply overriding the amount.

Differences may arise from unrecorded purchases, unprocessed returns, inaccurate stocktake counts, damaged goods, theft, internal use or data-entry errors.

Record purchases accurately

Separate inventory purchases from general operating expenses in your accounting software. Use meaningful categories so that product purchases, inbound freight, packaging and direct production costs can be reviewed separately where appropriate.

Where a supplier invoice includes both resale stock and other business items, split the transaction rather than allocating the entire invoice to one account.

Perform stocktakes and investigate variances

A physical stocktake remains valuable, even where the business uses inventory software. It tests whether the system reflects what is actually on hand.

Count stock carefully, document the process and investigate material discrepancies. A stock variance may be a sign of damaged goods, wastage, theft, supplier shortages, incorrect unit measurements or weaknesses in sales and receiving procedures.

Review slow-moving and obsolete stock

Not all inventory has the same commercial value. Products may become expired, superseded, damaged, seasonal or difficult to sell.

Regularly review items that have not moved for an extended period. Decisions may include discounting, bundling, returning goods to a supplier, repurposing materials or writing down stock where there is a supportable reason. This can improve both the quality of management reporting and purchasing decisions.

Compare your gross margin by product or category

Do not stop at one total COGS figure. Where your systems allow, review gross profit by:

  • Product line

  • Supplier

  • Sales channel

  • Customer group

  • Job or project

  • Location

  • Promotion or campaign

A total business margin may look acceptable while certain products, channels or jobs are consistently unprofitable.

Tax considerations for trading stock

COGS is a management and accounting measure, but it also has income tax implications. Businesses carrying on an enterprise with trading stock generally need to consider the value of stock on hand at the start and end of the income year.

The value of closing stock can affect taxable income, so it should be supported by accurate records and a defensible valuation approach. For businesses with obsolete, damaged or otherwise impaired stock, the tax rules include provisions that may allow a lower reasonable value in the right circumstances.

Some eligible small and medium business entities may be able to choose not to account for changes in trading stock for an income year where the difference between opening stock and a reasonable estimate of closing stock does not exceed $5,000. This is a simplification measure, not a reason to ignore stock controls altogether. Accurate internal inventory records can still be essential for pricing, cash flow and profitability.

Special care may also be needed where stock is:

  • Taken for private use

  • Given away or used for promotions

  • Lost, stolen or destroyed

  • Transferred between related entities

  • Sold below normal price

  • Imported from overseas suppliers

  • Converted from business use into trading stock, or vice versa

  • Included in a business sale, restructure or closure

These situations can have tax, GST and accounting consequences beyond a standard COGS calculation. They should be reviewed before entries are finalised.

Turning COGS insight into stronger margins

The purpose of calculating COGS is not simply to complete financial reports. It is to make better business decisions.

Once your figures are reliable, focus on the actions that can improve margin without undermining customer value:

  • Review selling prices after supplier cost changes.

  • Set a minimum gross-margin target for product lines or jobs.

  • Negotiate supplier pricing, freight arrangements and volume discounts.

  • Reduce over-ordering and focus purchasing on proven sellers.

  • Identify products with high returns, damage rates or handling costs.

  • Introduce stock controls for receiving, transfers, discounts and write-offs.

  • Review whether low-margin products encourage profitable follow-on sales or simply consume cash and time.

  • Measure promotions by gross profit, not sales volume alone.

Small improvements can be meaningful when they are applied consistently. A modest reduction in wastage, a better purchasing decision or a timely price adjustment may improve profitability more effectively than chasing additional sales at thin margins.

Make COGS part of your regular financial review

A reliable COGS calculation turns inventory data into practical business insight. It helps you see what has actually been sold, what it cost to provide, how much gross profit remains and where margins may be slipping.

For Australian businesses that buy, make or sell products, COGS should be reviewed regularly, not treated as an EOFY exercise. The more quickly you can identify changes in stock costs, shrinkage, pricing or product performance, the sooner you can respond.

This article is general information only and is not personal financial or tax advice. COGS, trading stock and GST treatment can vary depending on your business structure, industry, accounting methods and circumstances. Speak with a registered tax agent or accountant, such as, for advice tailored to your business.