Inventory Price Index Computation (IPIC) Method Under LIFO

The IPIC method under LIFO is an IRS-sanctioned way to value dollar-value LIFO inventory using the Bureau of Labor Statistics’ published price indexes instead of internally tracked base-year costs. Authorized by Section 472(f) of the Internal Revenue Code and detailed in Treasury Regulation 1.472-8(e)(3), the Inventory Price Index Computation method lets a business measure inflation in its inventory pools with CPI or PPI data, which cuts the record-keeping load that makes other LIFO techniques impractical for companies stocking thousands of SKUs.¹ Because the IRS accepts BLS data as an objective inflation measure, IPIC calculations tend to hold up under audit and give businesses a repeatable way to compute LIFO adjustments each year.

Why Businesses Choose IPIC Over Other LIFO Methods

Traditional dollar-value LIFO methods like double extension require a business to track both the base-year cost and the current-year cost of every item in inventory, then compute its own price index from that internal data. For retailers and distributors cycling through thousands of items, that becomes unmanageable. IPIC pulls inflation data directly from BLS consumer and producer price indexes, so you never have to maintain base-year unit costs for individual items.

The regulations also give IPIC users a flexibility that non-IPIC LIFO taxpayers do not have. An IPIC user can compute the pool-level index using either the double-extension approach or the link-chain approach without first having to show that double extension is impractical.² Under non-IPIC dollar-value LIFO, that showing is generally required before you can move to link-chain. Link-chain IPIC is popular because it multiplies the current year’s weighted category inflation index by the prior year’s cumulative index, creating a rolling measurement that handles product turnover cleanly.

Who Can Elect IPIC

Any taxpayer using dollar-value LIFO can elect IPIC. The regulations specifically contemplate its use by manufacturers, processors, wholesalers, jobbers, distributors, and retailers.² Once you adopt IPIC for a specific trade or business, it must be used for all dollar-value LIFO inventory in that trade or business. You cannot apply IPIC to some pools and a different LIFO method to others in the same operation.

IPIC pooling rules also permit broader inventory groupings than other LIFO techniques. You can often group all goods within a single BLS major commodity group into one pool. Retailers using the retail inventory method pool goods by CPI expenditure category; manufacturers usually keep separate pools for raw materials and finished goods based on PPI commodity groups. Fewer pools means less administration and less risk that a small, volatile category distorts the overall index.

Check the Small Business Inventory Exemption First

Before committing to any LIFO system, confirm whether Section 471(c) makes the exercise unnecessary. If your average annual gross receipts over the prior three tax years do not exceed $32 million for tax years beginning in 2026, and you are not a tax shelter, you are not required to use traditional inventory accounting at all.³ A qualifying business can instead treat inventory as non-incidental materials and supplies or conform to the method used in its financial statements.⁴ For many mid-size companies, that is cheaper than building an IPIC calculation.

Which BLS Tables Feed the Calculation

IPIC pulls its inflation data from two BLS publications: the CPI Detailed Report and the PPI Detailed Report. Which one applies depends on the type of business.

Manufacturers, processors, wholesalers, jobbers, and distributors must use Table 6 of the PPI Detailed Report, which covers commodity groupings and individual items on a not-seasonally-adjusted basis. A different PPI table may be used only if the taxpayer can demonstrate it is more appropriate for the inventory in question.
Retailers may choose between Table 3 of the CPI Detailed Report and Table 6 of the PPI Detailed Report. Retailers using the retail inventory method typically find CPI Table 3 a better fit because it tracks prices at the consumer level.

These assignments come directly from the regulation.² The BLS also periodically reorganizes its tables. When category structures or base-year indexes change, the regulations require you to compute affected category indexes using a reasonable method applied consistently across all affected categories for that tax year.⁵

Picking a Representative Month

The BLS publishes index data monthly, so you must decide which month’s numbers feed your calculation. The default for taxpayers not on the retail method is the month most consistent with the taxpayer’s purchasing or production patterns and its method of determining current-year cost. You may also make a one-time binding election on Form 970 to lock in a specific representative month for each pool.² That election is a method of accounting: once made, it must be used every year unless the IRS consents to a change or revocation.⁵

Mapping Inventory to BLS Categories

Every item in inventory has to be assigned to a BLS category. The general rule is to assign each item to the most detailed BLS category that includes it. Manufacturers assign raw materials to the most detailed PPI category covering that material and finished goods to the most detailed PPI category covering the finished product. Work-in-process items go to the category of the finished good they will become.⁵

Item-by-item mapping is heavy work for businesses with large or diverse inventories. The regulations offer an alternative called the 10 percent method, which runs in three steps.

Step one. If a single item’s current-year cost is 10 percent or more of the pool’s total current-year cost, assign that item to its most detailed BLS category. Other items falling into that same category are pulled in automatically.
Step two. For items not yet assigned, move to successively less detailed BLS categories until unassigned items taken together account for at least 10 percent of the pool’s current-year cost. Repeat until all items are assigned or the remaining items total less than 10 percent.
Step three. If leftover items collectively represent less than 10 percent of the pool, assign them all to the most detailed BLS category that covers them. If no single category fits, create a miscellaneous category.

Whichever approach you use, no item may be assigned to a BLS category less detailed than a major group in CPI Table 3 or a major commodity group in PPI Table 6.⁶ The 10 percent method is an election, and once made, it becomes part of your accounting method.

How the Pool Index Is Computed

With items mapped and index data pulled for your chosen month, the calculation follows a set sequence. You compute a category inflation index for each selected BLS category by dividing the current-year BLS price index by the base-year index (or, under link-chain, the prior-year index). Those category inflation indexes are then combined into a single pool-level inventory price index.

Under link-chain IPIC, the pool-level IPI is the weighted harmonic mean of the category inflation indexes, with weights equal to current-year costs in each BLS category, multiplied by the prior year’s cumulative IPI.² Double-extension IPIC uses a similar computation but references the original base year directly rather than chaining year over year.

Divide the pool’s total current-year cost by the IPI to get the pool’s base-year cost. Compare that figure to the prior year’s base-year cost: an increase produces a new LIFO layer (an increment); a decrease is a liquidation of older layers. A new layer is valued at the current year’s IPI. That layering is what defers income during inflationary periods.

How to Elect IPIC

How you make the election depends on whether you are new to LIFO or already on it.

New LIFO Adopters

If you have never used LIFO before, elect LIFO and the IPIC method together on Form 970 (Application to Use LIFO Inventory Method), attached to your federal income tax return for the first year LIFO applies. The form calls for an analysis of your beginning and ending inventories for the election year plus beginning inventory for the prior year. Manufacturers must break their inventory into natural groups based on production processes, raw materials, or finished product characteristics.⁷ Specify on Form 970 that you are electing IPIC, identify the BLS table you are using, and note the representative month election if you are making one.

Switching From Another LIFO Method

A business already on LIFO that wants to move to IPIC is changing its accounting method and must file Form 3115 (Application for Change in Accounting Method). Revenue Procedure 2025-23 provides a designated automatic change number for the switch from a non-IPIC LIFO method to IPIC and for updating from the older IPIC rules to the current regulatory framework.⁸ A duplicate copy of Form 3115 must be mailed to the IRS at its Ogden, Utah processing center (M/S 6111).⁹

Both forms attach to a timely filed return, including extensions. Keep copies permanently. The IRS does not always send an approval letter, so the filed return and attached form are your evidence that the method is in place.

Section 481(a) Adjustment When Switching In

Changing inventory methods generally requires an adjustment under Section 481(a) to prevent income from being counted twice or skipped. The adjustment equals the cumulative difference between inventory valued under your old method and inventory valued under your new method as of the first day of the year of change.¹⁰

How the adjustment enters income depends on direction and whether the change is voluntary.

Negative adjustment (reduces income): taken entirely in the year of change.
Positive adjustment, voluntary change: spread over four tax years starting with the year of change. If the adjustment is less than $50,000, you can elect to take it all in one year.
Positive adjustment, IRS-imposed change: the entire amount hits the year of change, with no spreading.

Changes made within LIFO, such as moving from one LIFO pooling approach to another while staying on LIFO, are generally implemented on a cut-off basis. Under that approach, only items arising on or after the beginning of the change year use the new method, and no 481(a) adjustment is needed.¹⁰ Initial adoption of LIFO from a non-LIFO method like FIFO, however, does typically trigger the adjustment.

Watch the LIFO Conformity Rule

Using LIFO on your tax return carries a condition: you cannot use a different inventory method for credit purposes or in reports to shareholders, partners, or beneficiaries. That is the LIFO conformity requirement, and violating it can cost you the entire LIFO election.¹¹

The regulation does allow a non-LIFO method in supplemental or explanatory disclosures (clearly labeled as such), in balance sheet asset valuations, in internal management reports, and in interim reports covering less than a full tax year. Using the lower of LIFO cost or market for financial reports is also permitted.¹¹

If the IRS determines you violated conformity, consequences are severe. The Commissioner can terminate the LIFO election, which triggers a 481(a) adjustment equal to your entire LIFO reserve as of the beginning of the year of change. You lose access to special relief provisions for that adjustment, so the full amount hits income without favorable spreading. And you generally cannot re-elect LIFO for at least five tax years after termination.¹² Many LIFO problems start here: a finance team prepares FIFO-based reports for a bank loan without recognizing the conformity implications.

Records You Must Keep

LIFO recordkeeping is stricter than most businesses expect, and the IRS has stated that inadequate documentation alone can justify terminating a LIFO election. Maintain the following for as long as your LIFO election remains in effect:

Detailed current cost listings for every year, including SKU number, item description, quantity on hand at year-end, and unit cost.
Base cost records: the detailed cost listing from the year before your LIFO election began, adjusted to reflect inventory at cost with any prior write-downs restored.
Index determinations: records showing how you computed each category inflation index and each pool-level IPI.
Double-extension or link-chain workpapers connecting current-year costs to base-year costs.
Supporting documents: invoice documentation of unit costs, plus copies of Form 970 and any Form 3115 filings.

Current cost listings and base cost records must be kept for the entire duration of the LIFO election, not just the standard statute-of-limitations period. Invoice documentation follows the normal retention rule and must be kept for the statute of limitations plus any extensions.¹³ For a company that has used LIFO for 20 years, that means 20 years of annual inventory detail in accessible storage.

1
Office of the Law Revision Counsel. 26 USC 472 – Last-In, First-Out Inventories
2
eCFR. 26 CFR 1.472-8 – Dollar-Value Method of Pricing LIFO Inventories
3
Internal Revenue Service. Revenue Procedure 2025-32
4
Office of the Law Revision Counsel. 26 USC 471 – General Rule for Inventories
5
Federal Register. Dollar-Value LIFO Regulations; Inventory Price Index Computation Method
6
eCFR. 26 CFR 1.472-8 – Dollar-Value Method of Pricing LIFO Inventories
7
eCFR. 26 CFR 1.472-3 – Time and Manner of Making Election
8
Internal Revenue Service. Revenue Procedure 2025-23
9
Internal Revenue Service. Where to File Form 3115
10
Internal Revenue Service. IRM 4.11.6 – Changes in Accounting Methods
11
eCFR. 26 CFR 1.472-2 – Requirements Incident to Adoption and Use of LIFO Inventory Method
12
Internal Revenue Service. Adopting LIFO Practice Unit
13
Internal Revenue Service. LIFO Records