FIFO Inventory Method: What It Is, How It Works, and When to Use It

If you sell physical products, your inventory is likely one of your largest assets. How you value that inventory directly affects your cost of goods sold, your reported profit, and ultimately how much you owe in taxes. Yet many small business owners pick an inventory method almost at random—or worse, don't realize they have a choice at all.

FIFO, which stands for First In, First Out, is the most widely used inventory valuation method in the world. Roughly 55% of companies use it as their primary method. In this guide, we'll break down exactly how FIFO works, walk through a real calculation, compare it to other methods, and help you decide whether it's the right fit for your business.

What Is the FIFO Method?

FIFO is an inventory costing method that assumes the oldest items in your inventory are sold first. When you calculate your cost of goods sold (COGS), you assign the cost of your earliest purchases to those sales before moving on to more recent purchases.

It's important to understand that FIFO is an accounting assumption, not a requirement for how you physically move products. You don't have to literally sell your oldest stock first (though for perishable goods, you should). FIFO simply determines which costs get assigned to items you sell versus items that remain in inventory.

Here's the core principle: oldest costs go to COGS, newest costs stay on the balance sheet.

How FIFO Works: A Step-by-Step Example

Let's say you run an online store selling handmade candles. During January, you make the following purchases:

Date	Units Purchased	Cost per Unit	Total Cost
Jan 5	100 candles	$8.00	$800
Jan 12	150 candles	$8.50	$1,275
Jan 22	120 candles	$9.00	$1,080

Total inventory available: 370 candles costing $3,155

Now let's say you sell 200 candles during January. Under FIFO, here's how you calculate COGS:

Step 1: Use the oldest batch first. All 100 candles from Jan 5 at $8.00 = $800

Step 2: You still need to account for 100 more units sold. Take the next oldest batch: 100 of the 150 candles from Jan 12 at $8.50 = $850

Step 3: Add them up. Total COGS = $800 + $850 = $1,650

Your ending inventory consists of:

• 50 remaining candles from Jan 12 at $8.50 = $425
• 120 candles from Jan 22 at $9.00 = $1,080
• Total ending inventory = $1,505

You can verify: $1,650 (COGS) + $1,505 (ending inventory) = $3,155 (total cost of goods available). The numbers balance.

Why FIFO Matters for Your Financial Statements

The inventory method you choose ripples through your entire financial picture. Here's how FIFO specifically affects your business:

Impact on Your Income Statement

COGS is one of the largest expenses on most product-based businesses' income statements. Since FIFO assigns older (often lower) costs to COGS during periods of rising prices, it typically results in:

• Lower COGS compared to LIFO
• Higher gross profit
• Higher net income

This makes your business look more profitable on paper, which can be attractive when seeking investors or applying for loans.

Impact on Your Balance Sheet

Because the newest (and often most expensive) inventory costs remain on the balance sheet, FIFO generally provides a more accurate picture of what your inventory is actually worth at current market prices. Lenders and investors tend to prefer this because it's closer to the replacement cost of your inventory.

Impact on Your Taxes

Here's where FIFO has a tradeoff. Higher reported income means a larger tax bill. When costs are rising, FIFO produces more taxable income than LIFO would. For some businesses, this is a significant consideration—though it has to be weighed against the benefits of stronger financial statements.

FIFO vs. LIFO: Understanding the Key Differences

LIFO (Last In, First Out) is the opposite of FIFO. It assumes the most recently purchased items are sold first. Here's a side-by-side comparison:

Factor	FIFO	LIFO
Cost assigned to COGS	Oldest costs first	Newest costs first
Ending inventory value	Reflects recent prices	Reflects older prices
Net income (rising prices)	Higher	Lower
Tax liability (rising prices)	Higher	Lower
Balance sheet accuracy	More accurate	Less accurate
GAAP compliant	Yes	Yes
IFRS compliant	Yes	No
Global acceptance	Worldwide	US only

A few critical points:

• IFRS prohibits LIFO entirely. If your business operates internationally or plans to, FIFO is the safer choice.
• LIFO can create phantom inventory. Old costs sitting on the balance sheet for years can wildly understate your true inventory value.
• Switching methods requires IRS approval. You'll need to file Form 3115 (Application for Change in Accounting Method), and the change may trigger adjustments to your taxable income.

FIFO vs. Weighted Average Cost

The weighted average cost method takes a different approach entirely. Instead of tracking individual batches, it calculates a single average cost per unit across all inventory.

Using our candle example:

• Total cost: $3,155
• Total units: 370
• Weighted average cost per unit: $3,155 / 370 = $8.53
• COGS for 200 candles: 200 x $8.53 = $1,706

Compare that to FIFO's COGS of $1,650. The weighted average method falls between FIFO and LIFO in most scenarios.

When weighted average makes sense:

• You mix raw materials together (like a paint manufacturer)
• Tracking individual batches is impractical
• You want simpler record-keeping

When FIFO is better:

• You sell distinct, identifiable products
• You deal with perishable goods
• You want your balance sheet to reflect current market values
• You operate internationally

When Should You Use FIFO?

FIFO is particularly well-suited for these situations:

Perishable Goods

If you sell food, cosmetics, pharmaceuticals, or anything with an expiration date, FIFO aligns your accounting with how you should already be managing your physical inventory. Selling oldest stock first reduces waste and spoilage.

Rising Costs

When your supplier prices are trending upward, FIFO keeps your balance sheet inventory valuation close to current replacement costs. This gives stakeholders a more realistic view of your assets.

International Business

Since IFRS doesn't allow LIFO, companies that report under international standards or plan to expand globally should use FIFO to avoid costly accounting method changes later.

Seeking Funding

FIFO typically produces higher net income and a stronger balance sheet. If you're pitching to investors or applying for bank financing, these healthier-looking financials can work in your favor.

Simplicity

For most small businesses, FIFO is intuitive. It mirrors how most people naturally think about inventory: sell the old stuff first. This makes it easier to understand and explain to partners, accountants, and tax advisors.

Common FIFO Mistakes to Avoid

Not Tracking Purchase Batches

FIFO requires you to know when each batch was purchased and at what cost. If you're tossing all inventory into one mental bucket, you can't accurately apply FIFO. Use your accounting software's inventory tracking features to maintain proper batch records.

Ignoring the Tax Impact

Don't choose FIFO purely because it makes your income statement look good. Run the numbers on both FIFO and LIFO (or weighted average) to understand the actual tax difference. For some businesses, the tax savings from LIFO outweigh the reporting benefits of FIFO.

Switching Methods Without Planning

The IRS requires consistency in your inventory method. If you want to switch from LIFO to FIFO (or vice versa), you need to file Form 3115 and may face a taxable income adjustment. Talk to your accountant before making any changes.

Confusing Accounting Method with Physical Flow

Remember, FIFO is a cost assignment method. Your warehouse might ship from whichever shelf is most convenient—that's fine. FIFO only governs which costs appear on your financial statements, not how you physically fulfill orders.

How to Implement FIFO in Your Business

Getting started with FIFO is straightforward:

1. Record each purchase as a separate layer. Every time you buy inventory, log the date, quantity, and unit cost.

2. When you sell, deplete the oldest layer first. Assign the cost of your earliest purchase to the sale. Once that layer is exhausted, move to the next.

3. Calculate ending inventory from the newest layers. Whatever remains unsold carries the most recent purchase costs.

4. Reconcile regularly. At minimum, verify your calculated ending inventory against a physical count at least quarterly.

5. Use software. Most modern accounting and inventory management tools support FIFO calculations automatically. Manual spreadsheets work for very small operations but become error-prone as you scale.

Keep Your Inventory Records Organized from Day One

Choosing the right inventory valuation method is just one piece of the puzzle. The real challenge is maintaining accurate, consistent records as your business grows. Whether you're tracking 50 SKUs or 5,000, having a reliable system for recording purchases, sales, and inventory movements makes everything easier—from filing taxes to securing financing.

Beancount.io provides plain-text accounting that gives you complete transparency and control over your financial data, including inventory tracking. With version-controlled records and no vendor lock-in, you always know exactly where your numbers come from. Get started for free and see why developers and finance professionals trust plain-text accounting for their most important financial decisions.