What is inventory accounting? A guide for small businesses

Published Monday 15 June 2026

Table of contents

• What is inventory?
• What is inventory accounting?
• Types of inventory
• Inventory accounting methods
• How to calculate cost of goods sold (COGS)
• Periodic vs. perpetual inventory systems
• Benefits of inventory accounting
• How to record inventory transactions
• Inventory performance metrics
• Inventory accounting compliance and GAAP rules
• Simplify your inventory accounting with Xero
• FAQs on inventory accounting

Key takeaways

• Choose the right inventory valuation method for your business, such as FIFO, LIFO, weighted-average cost, or specific identification, and apply it consistently for accurate financial reporting and tax compliance.
• Record inventory purchases as current assets on your balance sheet, then transfer costs to the Cost of Goods Sold (COGS) expense account when items sell so your profit margins stay accurate.
• Track inventory performance metrics like turnover ratio and days inventory outstanding to spot slow-moving stock, reduce carrying costs, and free up cash flow.
• Understand the difference between periodic and perpetual inventory systems so you can pick the approach that fits your business size, volume, and budget.

What is inventory?

Inventory is the goods your business owns and intends to sell to customers for profit. You list these items as current assets on your balance sheet until they're sold.

Your inventory includes:

• raw materials: components used to create finished products
• work-in-progress (WIP): partially completed items still in production
• finished goods: completed products ready for sale
• items for resale: products bought specifically to sell without modification

Equipment, supplies, and tools you use to run your business aren't inventory; they're business expenses. If you run an ecommerce business and a third party ships goods directly to your customer, you don't have inventory. Only goods you own and hold for sale count as inventory.

What is inventory accounting?

Inventory accounting is the process of tracking, valuing, and managing your inventory from purchase to sale. It helps you understand the true cost and value of goods you own, so you can set profitable prices, stay compliant with tax rules, and make confident business decisions.

Inventory accounting matters for your business in several ways:

• accurate pricing: know your true costs so you can set profitable selling prices
• tax compliance: report inventory values correctly on your IRS returns
• cash flow management: track money tied up in unsold goods
• insurance coverage: document inventory values for proper coverage
• business valuation: show accurate asset values to lenders or buyers
• profit analysis: identify which products generate the most profit

Types of inventory

Inventory falls into 4 main categories. Knowing each type helps you track what you have on hand and how to account for it.

• Raw materials: the basic components you use to create your products. For a bakery, raw materials include flour, sugar, and eggs.
• Work-in-progress (WIP): partially finished items not yet ready for sale. For example, dough that's rising before baking.
• Finished goods: completed products ready to sell, such as freshly baked bread on the shelf.
• Maintenance, repair, and operations (MRO): items that help you run your business but aren't part of your final product, such as cleaning supplies or packing boxes.

For a deeper look at each category, see 4 types of inventory.

Inventory accounting methods

How you value your inventory affects your balance sheet, income statement, and tax bill. There are 4 common methods for tracking the cost of goods sold (COGS), and each one suits different types of businesses.

First-In, First-Out (FIFO) assumes the oldest items you bought are the first ones you sell. This method works well if you sell perishable goods, such as food, because it matches the natural flow of stock. Under current US Generally Accepted Accounting Principles (GAAP), FIFO inventory is valued at the lower of cost and net realizable value (NRV).

Last-In, First-Out (LIFO) assumes you sell the most recently purchased items first. This can lower your taxable income during periods of rising prices because it matches higher-cost inventory against revenue. LIFO is allowed under US GAAP; you must elect it by filing Form 970 under Internal Revenue Code section 472. International Financial Reporting Standards (IFRS) do not allow LIFO.

Weighted-Average Cost (WAC) divides the total cost of all goods available for sale by the total number of units. This smooths out price fluctuations and works well for businesses that sell large quantities of similar items. Like FIFO, WAC inventory is valued at the lower of cost and net realizable value under current GAAP rules.

Specific Identification tracks the actual cost of each individual item. It's best suited for businesses that sell unique, high-value products such as custom furniture, vehicles, or fine jewelry. Because you assign the exact purchase cost to each unit sold, this method gives you the most precise COGS figure, but it requires detailed record keeping.

How to calculate cost of goods sold (COGS)

Cost of Goods Sold (COGS) represents the direct costs of producing or purchasing the items you sold during a period. Calculating COGS accurately is essential for understanding your gross profit and filing your tax return.

The basic COGS formula is:

Beginning Inventory + Purchases - Ending Inventory = COGS

To see how the formula works, consider this example. Say you run a small retail shop:

1. Your beginning inventory on January 1 is valued at $20,000.
2. During the quarter, you purchase $15,000 worth of new stock.
3. On March 31, you count your remaining inventory and value it at $12,000.

Your COGS for the quarter is: $20,000 + $15,000 - $12,000 = $23,000. That means you spent $23,000 on the goods you actually sold, and your gross profit equals your revenue minus that $23,000.

The inventory valuation method you choose (FIFO, LIFO, weighted-average cost, or specific identification) determines how you assign costs to ending inventory and COGS. Different methods can produce different profit figures from the same transactions, so pick a method and stick with it consistently.

Periodic vs. perpetual inventory systems

The system you use to track inventory determines how often your records are updated and how much manual work is involved. There are 2 main approaches: periodic and perpetual.

A periodic inventory system updates your inventory records at set intervals, such as monthly or quarterly. You conduct a physical count at the end of each period, then calculate COGS using the formula above. This approach is simpler and less expensive to maintain, making it a practical choice for small businesses with lower sales volumes or limited product lines.

A perpetual inventory system updates your records in real time every time you buy or sell an item. Each purchase increases your inventory account, and each sale automatically reduces it. This gives you up-to-the-minute visibility into stock levels and COGS without waiting for a physical count.

Perpetual systems require an inventory management system or accounting software to track every transaction. The upfront cost is higher, but you get more accurate data and can spot issues like shrinkage or stockouts faster.

Many small businesses start with a periodic system and move to perpetual as they grow. Either way, regular physical counts remain important for verifying that your records match what's actually on the shelves.

Benefits of inventory accounting

Good inventory accounting helps you save money, increase profits, and make smarter decisions across your business.

Revenue optimization

Keeping accurate inventory records helps you protect and grow your revenue.

• Prevent stockouts: keep items in stock so you don't miss sales opportunities
• Identify bestsellers: focus resources on your highest-performing products
• Plan seasonal promotions: use sales data to time marketing campaigns for maximum impact

Cost reduction

Tracking inventory costs closely helps you cut unnecessary spending.

• Minimize storage costs: order optimal quantities to reduce warehousing expenses
• Avoid write-offs: spot slow-moving items early so you can discount or liquidate them
• Negotiate better rates: use purchasing data to secure bulk discounts from suppliers

Financial management

Accurate inventory data strengthens your financial position and planning.

• Improve cash flow: reduce money tied up in excess inventory. With US small businesses waiting an average of 27.9 days to be paid, and payments arriving 7.8 days late in Q4 2025, managing the cash locked in unsold stock is more important than ever, according to Xero Small Business Insights.
• Track profit margins: monitor true product costs for better pricing decisions
• Manage tax obligations: time purchases strategically to reduce your tax burden

In 2025, US small business sales growth averaged just 2.4% year-over-year, less than half the long-term average of 5.5%, according to Xero Small Business Insights. In a slower growth environment, optimizing inventory costs becomes a key lever for protecting margins.

How to record inventory transactions

Recording inventory correctly keeps your financial statements accurate and your tax filings on track. Here's how to handle the most common inventory transactions.

1. Record the purchase. When you buy inventory, debit your inventory asset account and credit cash or accounts payable. This adds the item's cost to your balance sheet as a current asset.
2. Record the sale. When you sell an item, you need 2 entries. First, record the revenue by debiting accounts receivable (or cash) and crediting sales revenue. Then move the item's cost from inventory to expenses by debiting Cost of Goods Sold (COGS) and crediting inventory.
3. Record returns. If a customer returns an item, reverse the sale entry: debit sales returns and credit accounts receivable, then debit inventory and credit COGS to put the item back on your books.
4. Record adjustments. After a physical count, adjust your records for any differences. If your actual count is lower than your books show, debit an inventory shrinkage expense and credit inventory.
5. Review your records regularly. Compare your physical inventory counts to your accounting records at least quarterly. Regular reconciliation catches errors early and keeps your financial statements reliable.

Inventory performance metrics

Tracking the right metrics helps you understand how efficiently your business manages stock. 2 key metrics to monitor are inventory turnover ratio and days inventory outstanding.

Inventory turnover ratio

Inventory turnover measures how many times you sell and replace your inventory during a period.

The formula is: Inventory Turnover = Cost of Goods Sold / Average Inventory

For example, if your annual COGS is $120,000 and your average inventory is $30,000, your turnover ratio is 4. That means you sold through your entire stock 4 times during the year.

A higher turnover ratio generally signals strong sales and efficient inventory management. A low ratio may mean you're carrying too much stock, tying up cash that could be used elsewhere. What counts as "good" varies by industry, so compare your ratio to benchmarks in your sector.

Days inventory outstanding

Days inventory outstanding (DIO) tells you the average number of days it takes to sell your inventory.

The formula is: DIO = (Average Inventory / Cost of Goods Sold) x 365

Using the same example: ($30,000 / $120,000) x 365 = 91.25 days. On average, it takes about 91 days to sell through your stock.

A lower DIO means you're converting inventory to cash faster. If your DIO is climbing, it may be time to review purchasing patterns, run promotions on slow-moving items, or adjust your product mix.

Inventory accounting compliance and GAAP rules

Following consistent accounting standards keeps your financial reports reliable and helps you stay on the right side of tax rules. In the US, most businesses follow Generally Accepted Accounting Principles (GAAP) for inventory.

Consistency principle

GAAP requires you to use the same inventory valuation method from period to period. If you start with FIFO, stick with FIFO. Switching methods requires disclosure and, in some cases, IRS approval. Consistent valuation helps lenders and investors trust your financial statements.

Lower of cost and net realizable value

Under ASU 2015-11, inventory measured using FIFO or weighted-average cost must be reported at the lower of cost and net realizable value (NRV). NRV is the estimated selling price minus the costs to complete and sell the item. If your inventory's market value drops below what you paid, you write it down to NRV on your balance sheet.

For inventory measured using LIFO or the retail inventory method, the older "lower of cost or market" rule still applies.

IRS small business exemption

If your average annual gross receipts are $32 million or less (2026 tax year, adjusted annually for inflation under Section 448(c)), the IRS doesn't require you to follow the Uniform Capitalization (UNICAP) rules. This exemption simplifies inventory accounting for most small businesses.

Disclosure requirements

GAAP requires you to disclose the inventory valuation method you use, total inventory value, and any write-downs in your financial statements. If you change your valuation method, you must disclose the change and its impact on your financials.

IFRS comparison

International Accounting Standard (IAS) 2 also requires inventory to be measured at the lower of cost and net realizable value. The key difference is that IFRS does not allow LIFO. If your business operates internationally, you may need to reconcile these differences.

Simplify your inventory accounting with Xero

Setting up inventory accounting doesn't have to be complicated. With the right tools, you can automate much of the tracking and focus on growing your business instead.

Follow these steps to get started with Xero:

1. Choose your valuation method: select FIFO, LIFO, weighted-average cost, or specific identification based on your product type and industry.
2. Set up your chart of accounts: create inventory asset, COGS, and sales revenue accounts in Xero so transactions flow to the right places.
3. Add your products: enter each inventory item with its cost, selling price, and quantity on hand.
4. Connect your bank feeds: link your bank account so purchases and payments reconcile automatically.
5. Schedule regular counts: set reminders for physical inventory counts to verify your records match what's on the shelves.
6. Review your reports: use Xero's profit and loss and balance sheet reports to monitor inventory costs, margins, and cash flow.

Xero's cloud accounting platform tracks inventory transactions, calculates COGS, and generates reports so you spend less time on manual bookkeeping and more time running your business. Connect apps from the Xero App Store for deeper small business accounting and inventory management as you grow. Get one month free to see how easy it is.

FAQs on inventory accounting

Here are frequently asked questions about inventory accounting to help you get started.

What are the 4 types of inventory?

The 4 main types of inventory are raw materials, work-in-progress (WIP), finished goods, and maintenance, repair, and operations (MRO) items. Each type is tracked differently depending on where it sits in your production or sales process.

How do you record inventory in accounting?

When you buy inventory, record it as a current asset on your balance sheet. When you sell it, move its cost from the inventory asset account to the cost of goods sold (COGS) expense account.

What are the GAAP rules for inventory?

GAAP requires you to use the same valuation method consistently and report inventory at the lower of cost and net realizable value for FIFO and weighted-average cost methods. For LIFO inventory, the older lower of cost or market rule still applies.

What's the difference between periodic and perpetual inventory systems?

A periodic system updates inventory records at set intervals through physical counts, while a perpetual system tracks every transaction in real time. Periodic is simpler and cheaper; perpetual gives you up-to-the-minute stock visibility.

What is inventory turnover and why does it matter?

Inventory turnover measures how many times you sell and replace stock during a period. A higher ratio signals efficient inventory management and strong sales, while a low ratio may mean you're tying up cash in excess stock.

How do you calculate cost of goods sold?

Use the formula: Beginning Inventory + Purchases - Ending Inventory = COGS. The valuation method you choose (FIFO, LIFO, weighted-average cost, or specific identification) determines how costs are assigned to the items sold.