Accounting

ERP

Inventory Management

Inventory Costing Methods: FIFO, Average, Standard and Specific Identification in ERP

Sherman Hsieh

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Last updated: October 8, 2026 · Independent guide · We do not sell rankings or coverage.

Inventory costing methods decide which unit costs leave the balance sheet as cost of goods sold (COGS) and which stay in ending inventory. FIFO charges the oldest costs first, weighted average blends units into one cost, specific identification uses the exact cost of the unit shipped, and standard costing uses a preset cost plus variances. US GAAP accepts all four if applied consistently, but the tax rules differ and most ERPs lock the choice once an item is set up or used.

The rule and the journal entries

Every method uses one identity: beginning inventory + purchases − ending inventory = COGS.

• FIFO: COGS takes the oldest cost layers first; ending inventory holds recent prices.
• Weighted average: unit cost = (cost of beginning inventory + cost of purchases) ÷ (beginning units + units purchased). A moving average recalculates after every receipt.
• Specific identification: COGS is the actual recorded cost of the serial number or lot you shipped.
• Standard: inventory and COGS are recorded at a predetermined cost. Purchase price variance = (actual price − standard price) × quantity received.

In a perpetual system the method changes the amounts, not the accounts:

Worked example: one part, one month

Illustration: a distributor stocks a pump seal and has these January movements.

1. January 1: 100 units on hand at $40 = $4,000.
2. January 10: buys 200 units at $44 = $8,800.
3. January 20: buys 100 units at $50 = $5,000.
4. January 25: ships 250 units to a customer for $80 each = $20,000 of revenue.

Goods available total 400 units and $17,800. The sale follows both receipts, so periodic and perpetual results match.

Step 1, FIFO. The 250 units come from the oldest layers: 100 × $40 + 150 × $44 = $10,600 of COGS. Ending inventory is 50 × $44 + 100 × $50 = $7,200.

Step 2, weighted average. $17,800 ÷ 400 = $44.50 per unit. COGS is 250 × $44.50 = $11,125, and ending inventory is 150 × $44.50 = $6,675.

Step 3, specific identification. The warehouse picked 60 units from the January 1 lot, 120 from January 10 and 70 from January 20. COGS is $2,400 + $5,280 + $3,500 = $11,180, and ending inventory is $6,620.

Step 4, LIFO. US tax law still permits LIFO, so it is shown for comparison. The newest layers go first: 100 × $50 + 150 × $44 = $11,600 of COGS, leaving $6,200 in inventory.

With rising prices, FIFO reports $1,000 more gross profit, and taxable income, than LIFO from the same physical flow.

Step 5, standard costing. Assume a $45 standard set last year, so the opening 100 units sit at $4,500. Receipts post at standard:

The net variance is $300 unfavorable. Ending inventory ($6,750) is 37.5% of the $18,000 of standard cost in inventory and COGS, so a pro rata allocation moves $112.50 into inventory and $187.50 into COGS, bringing inventory close to actual cost as GAAP and the tax rules below expect. For variance types and when standard costing fits, see our guide to standard cost vs actual cost.

What GAAP and the IRS require

US GAAP (ASC 330)

PwC’s Inventory guide (partially updated April 2025) says cost may be determined using cost flow assumptions such as FIFO, average cost or LIFO, applied consistently. KPMG’s Inventory executive summary (October 2025) also lists specific identification as a cost flow assumption. Standard cost is acceptable if standards are updated at reasonable intervals and variances are absorbed so that standard cost approximates actual cost at the balance sheet date.

Every method except LIFO and the retail method uses the lower of cost and net realizable value (NRV) under ASC 330-10-35; LIFO and retail use lower of cost or market. A year-end write-down creates a new cost basis you cannot write back up (ASC 330-10-35-14). Changing your cost flow assumption is a change in accounting principle under ASC 250 that must be preferable, and preferability cannot be based on the tax effect alone.

Under IFRS, IAS 2 allows FIFO or weighted average for interchangeable items and specific identification for other items. LIFO is not among its cost formulas.

Federal tax

FIFO and specific identification. IRS Publication 538 (revised January 2022) describes both. Under 26 CFR 1.471-2(d), intermingled goods you cannot match to invoices are deemed the most recently purchased, a FIFO assumption.

Average cost. Rev. Proc. 2008-43 accepts a rolling average you also use for your books if you recompute it at least monthly and either stay within 1% of FIFO or specific identification or turn inventory at least four times a year.

Standard cost. 26 CFR 1.471-11(d)(3) allows standard cost for manufacturers if you reallocate a pro rata share of net variances to ending inventory.

LIFO. You elect it on Form 970 with the timely filed return for the first LIFO year. Under 26 CFR 1.472-2(e), you cannot report income to shareholders or creditors on a non-LIFO basis, although supplemental disclosures and internal reports are allowed. LIFO inventory is taken at cost regardless of market (1.472-2(b)). The Tax Adviser (February 18, 2026) notes that leaving LIFO reverses the reserve through a Section 481(a) adjustment, typically over four years.

Small business taxpayers. For tax years beginning in 2026, the Section 448(c) gross receipts test is $32 million (Rev. Proc. 2025-32). Publication 538 says eligible taxpayers that are not tax shelters can choose not to keep an inventory, though they still need a method, and are exempt from Section 263A uniform capitalization. Any change in tax inventory method requires Form 3115.

Common mistakes

• Writing every variance off to COGS. With stale standards, inventory no longer approximates actual cost, and 1.471-11 requires reallocation for tax.
• Treating the item setup as reversible. NetSuite, Business Central and QuickBooks Online all lock the method once items are saved or used (see the table below).
• Applying the wrong market test. LCNRV applies to FIFO, average and specific identification. LIFO and retail inventories use lower of cost or market.
• Breaking LIFO conformity. A FIFO-basis income statement sent to your lender for a LIFO year can put the election at risk.
• Using specific identification without the tracking to support it. Business Central requires item tracking on inbound and outbound transactions for its Specific method. Our guide to lot and serial tracking in ERP covers the setup.
• Treating book and tax inventory as one number. Section 263A additions and LIFO reserves create book-tax differences to track.

How to report it

Report inventory at cost under your method, reduced to NRV (or market, for LIFO) where needed, and state the basis and cost flow method in the notes. LIFO companies may show non-LIFO figures only as supplemental information.

Corporations and partnerships compute COGS on Form 1125-A (Rev. November 2024). Line 9a asks for your valuation method, line 9c whether you adopted LIFO (attach Form 970), line 9d your LIFO inventory and reserve, and line 9f whether quantities, cost or valuations changed between opening and closing inventory.

How ERP and accounting systems automate it

Oracle NetSuite. Average costing is the default, and NetSuite’s help notes that it uses the last purchase price as the costing method when inventory levels are negative. Specific costing uses the exact cost of the serial number you enter, and lot numbered costing assigns cost to a lot.

Business Central. Average cost can be calculated by day, week, month, quarter or accounting period, per item or per item, location and variant; changing that setting forces adjustment of affected entries. Microsoft says standard costing requires qualified maintenance.

Acumatica. Costs are calculated per warehouse. The documentation does not list LIFO, so a LIFO taxpayer would calculate it outside the system.

QuickBooks Online. If you create an inventory item before choosing, the account defaults to FIFO. Intuit lists no standard, LIFO or specific identification option.

For wider requirements, see our guide to ERP for inventory management.

How we researched this

On October 8, 2026 we read the IRS publications, forms and revenue procedures cited, the Treasury regulations on eCFR, PwC’s Inventory guide, KPMG’s Inventory executive summary and each vendor’s documentation, and reviewed the vendor and CPA firm pages that rank for this topic. The worked example uses invented figures. No vendor paid for inclusion.

Related guides

• COGS Journal Entry: Perpetual vs Periodic, With Examples
• Inventory Reconciliation: Count, Records and GL Tie-Out
• ABC Analysis in Inventory: Classify Items and Use Results

Frequently asked questions

Which inventory costing method is best for taxes?

When costs rise, LIFO usually gives the highest COGS and lowest taxable income, and FIFO the opposite. The trade-off is that you must also use LIFO in income statements for shareholders and lenders.

Can I use standard costing for my financial statements?

Yes, if you update standards at reasonable intervals and absorb variances so inventory approximates actual cost at the balance sheet date.

Can I change my inventory costing method?

For GAAP it is a change in accounting principle that must be preferable under ASC 250, and for tax you file Form 3115. Because ERPs lock the method per item, a change may also need new item records or, in Acumatica, zero on-hand stock.

When does specific identification make sense?

Use it when units or lots carry meaningfully different costs and you already scan serial or lot numbers, as with equipment or high-value components. For interchangeable stock, FIFO or average is simpler.

Sources

• IRS, Publication 538, Accounting Periods and Methods, revised January 2022. irs.gov
• IRS, Rev. Proc. 2025-32, Internal Revenue Bulletin 2025-45, November 3, 2025. irs.gov
• IRS, Rev. Proc. 2008-43, Internal Revenue Bulletin 2008-30, July 28, 2008. irs.gov
• IRS, Form 1125-A, Cost of Goods Sold, Rev. November 2024. irs.gov
• eCFR, 26 CFR 1.471-2, Valuation of inventories, up to date as of October 6, 2026. ecfr.gov
• eCFR, 26 CFR 1.471-11, Inventories of manufacturers, up to date as of October 6, 2026. ecfr.gov
• eCFR, 26 CFR 1.472-2, LIFO requirements, up to date as of October 6, 2026. ecfr.gov
• PwC (sells audit and advisory services), Inventory guide, partially updated April 2025. viewpoint.pwc.com
• KPMG (sells audit and advisory services), Inventory: Executive Summary, October 2025. kpmg.com
• The Tax Adviser (AICPA & CIMA), Why LIFO, why now?, Cindy Houser, CPA, CliftonLarsonAllen, February 18, 2026. thetaxadviser.com
• IFRS Foundation, IAS 2 Inventories, no date shown. ifrs.org
• Oracle NetSuite Help, Costing Methods, no date shown. docs.oracle.com
• Microsoft Learn, Design details: Costing methods (Business Central), March 17, 2026. learn.microsoft.com
• MYOB Acumatica user guide (MYOB resells Acumatica), Item Costs and Valuation Methods: General Information, no date shown. help.myob.com.au
• Intuit, Inventory valuation methods for cost accounting (QuickBooks Online), August 14, 2026. quickbooks.intuit.com

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Sherman Hsieh

CEO & Editor-in-Chief, Business-Software.com
Independent analysis of enterprise software — ERP, CRM and more

Sherman Hsieh is the founder, CEO, and editor-in-chief of Business-Software.com. He leads the site's independent, buyer-focused coverage of ERP, CRM, and other business systems, including vendor-neutral comparisons, pricing analysis, and implementation guidance. Before founding Business-Software.com, Sherman was an executive at Siebel ...