Inventory accounting is the process of tracking and valuing the products, materials, and supplies your business holds for sale or use in production. It determines how much of what you’ve purchased gets recorded as an expense (cost of goods sold) versus how much stays on your balance sheet as an asset you haven’t sold or used yet.

Your profit number depends on getting this right. Say you buy $80,000 in materials over the course of a year but only use $60,000 worth. Your cost of goods sold should be $60,000, not $80,000. The remaining $20,000 is inventory sitting in your warehouse or on your shelves. Without proper tracking, your profit and loss statement is wrong, and you’re either overpaying or underpaying on taxes. Neither situation is good.

The IRS requires businesses that produce, purchase, or sell merchandise to account for inventory. You can’t just expense everything when you buy it. You have to match the cost of goods to the revenue they generate. This matching principle is fundamental to accurate financial reporting.

There are a few common methods for valuing inventory. FIFO (First In, First Out) assumes the oldest inventory gets sold first and is the most common method for small businesses. LIFO (Last In, First Out) assumes the newest inventory gets sold first. Weighted average calculates an average cost across all units available for sale. The method you choose affects your reported profit and your tax liability, especially when prices are fluctuating. Once you pick a method, you need to stick with it consistently.

Beyond taxes, inventory accounting gives you real visibility into your business. You can see what’s moving, what’s sitting, and where your cash is tied up. A business might look profitable on paper but be cash-poor because too much money is locked in unsold product. Knowing your inventory levels and turnover helps you make smarter purchasing decisions and avoid tying up working capital in goods that aren’t selling.

This applies to more businesses than people realize. Retailers and e-commerce sellers are the obvious ones, but construction companies tracking materials by project, restaurants managing food costs, and any business that holds physical product all need some form of inventory accounting.

If your books currently expense everything at the time of purchase without accounting for what’s still on hand, your financial statements aren’t telling the full story. A QuickBooks ProAdvisor in Chandler can help you set up your system to track inventory properly so your margins are accurate, your purchasing decisions are informed, and your books are clean enough that your tax accountant can work with them confidently.