The way you value inventory directly affects your reported profit, your tax bill, and how investors read your books. Understanding FIFO vs LIFO is essential for any business that buys, makes, or sells physical products.
FIFO vs LIFO are two inventory accounting methods. FIFO (First In, First Out) assumes the oldest inventory sells first, while LIFO (Last In, First Out) assumes the newest inventory sells first. The choice changes your cost of goods sold, ending inventory value, and taxable income.
What is inventory accounting?
Inventory accounting is how a business assigns cost to the goods it holds and the goods it sells. Because prices change over time, the order in which you “flow” costs through your books affects your cost of goods sold (COGS) and your ending inventory value.
Those two figures drive your gross profit, which in turn affects your taxable income. That’s why the FIFO vs LIFO decision is more than an accounting technicality — it has real cash consequences.
FIFO explained (First In, First Out)
FIFO assumes the first items you purchased are the first ones sold. In a period of rising prices, that means your COGS reflects older, cheaper costs, while your ending inventory reflects newer, higher costs.
The result: FIFO generally produces higher reported profit and a higher inventory value on the balance sheet during inflation. It also mirrors how most businesses physically move goods — especially perishable products.
LIFO explained (Last In, First Out)
LIFO assumes the most recently purchased items are sold first. In a rising-price environment, your COGS reflects newer, higher costs, while ending inventory sits at older, lower costs.
The result: LIFO generally produces lower reported profit and a lower inventory value during inflation — which can mean a lower tax bill. Note that LIFO is permitted under US GAAP but is not allowed under IFRS, so internationally reporting companies often can’t use it.
FIFO vs LIFO: side-by-side comparison
The clearest way to grasp FIFO vs LIFO is to see how each method behaves under the same conditions.
| Factor | FIFO | LIFO |
|---|---|---|
| Cost flow assumption | Oldest costs first | Newest costs first |
| COGS during inflation | Lower | Higher |
| Reported profit during inflation | Higher | Lower |
| Ending inventory value | Higher (newer costs) | Lower (older costs) |
| Taxable income during inflation | Higher | Lower |
| Matches physical flow | Usually yes | Often no |
| Allowed under IFRS | Yes | No |
| Allowed under US GAAP | Yes | Yes |
A simple worked example
Imagine you buy 100 units at $10 each, then later buy 100 more at $15 each, and then sell 100 units.
- Under FIFO: COGS = 100 × $10 = $1,000. Ending inventory = 100 × $15 = $1,500.
- Under LIFO: COGS = 100 × $15 = $1,500. Ending inventory = 100 × $10 = $1,000.
Same purchases, same sale — but LIFO reports $500 more in COGS, which lowers profit and taxable income for the period. FIFO reports higher profit and a higher inventory value. This illustration is simplified; your actual results depend on volume, price movements, and your tax year.
Tax implications of FIFO vs LIFO
During inflation, LIFO can reduce taxable income by raising COGS, which is its main appeal in the US. However, the IRS enforces the “LIFO conformity rule”: if you use LIFO for taxes, you must also use it in your financial statements.
Switching methods isn’t casual either — changing your inventory valuation method generally requires IRS approval via Form 3115. Before you commit, fold the decision into your wider tax planning and confirm the current rules on IRS.gov.
Which method should your business choose?
There’s no universally “better” method — it depends on your goals, industry, and reporting requirements. Consider these factors:
- Choose FIFO if you sell perishable goods, report internationally under IFRS, or want financials that show stronger profit and inventory values.
- Choose LIFO if you operate only in the US, face rising costs, and want to reduce taxable income — provided the added complexity is worth it.
- Consider weighted average if you want a simpler middle-ground method that smooths price fluctuations.
Whichever you pick, accurate inventory valuation also affects which business deductions and cost figures you can support at tax time.
Recordkeeping and consistency
The IRS expects consistency. Once you adopt a method, you must apply it consistently from year to year unless you obtain permission to change. Keep detailed purchase records, dates, and quantities so your COGS calculation can withstand scrutiny.
Good inventory records also make audits, financing applications, and year-end close far less painful. Always verify current IRS requirements on IRS.gov, since accounting-method rules and forms can change.
Frequently asked questions about FIFO vs LIFO
What is the main difference between FIFO and LIFO?
The main difference in FIFO vs LIFO is the cost flow assumption. FIFO sells the oldest inventory first, so COGS uses older costs. LIFO sells the newest inventory first, so COGS uses recent costs. This changes profit, ending inventory value, and taxable income.
Is LIFO allowed under IFRS?
No. LIFO is prohibited under International Financial Reporting Standards (IFRS). It is permitted under US GAAP, which is why companies that report internationally typically use FIFO or the weighted-average method instead of LIFO.
Which method lowers taxes during inflation?
During periods of rising prices, LIFO generally lowers taxable income because it pushes newer, higher costs into cost of goods sold, reducing reported profit. FIFO produces higher profit and a higher tax bill in the same conditions. Confirm current tax rules on IRS.gov.
Can I switch from FIFO to LIFO?
Switching inventory accounting methods generally requires IRS approval, usually by filing Form 3115. You also can’t cherry-pick methods at will, and LIFO carries a conformity rule requiring its use in your financial statements too. Consult a professional before changing methods.
What is the LIFO conformity rule?
The LIFO conformity rule requires that if you use LIFO for your federal tax return, you must also use it in your financial statements presented to investors or creditors. FIFO does not carry this restriction, giving businesses more reporting flexibility.
Book a free consultation
Choosing the right inventory method can meaningfully change your tax bill and your financial picture. If you’re weighing FIFO vs LIFO or planning a method change, our team can model the impact and handle the paperwork. Book a free consultation with Tranzesta — supporting both US and UK clients with smart inventory and tax accounting.
Disclaimer: This article is for general informational purposes only and does not constitute tax, legal, or accounting advice. Tax rules and figures change and depend on your situation and tax year. Always verify current IRS figures and consult a qualified tax professional before acting.
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