Manufacturing Inventory Accounting and UNICAP: What IRC 263A Requires You to Capitalize

Most manufacturers understand that the raw steel, plastic, or fabric sitting on their shop floor is inventory. Fewer realize that the rent on the factory building, the electricity running the CNC machines, the depreciation on the production line, and even a share of the plant manager’s salary must also be folded into the cost of that inventory under IRC 263A. These are the Uniform Capitalization (UNICAP) rules, and they exist to prevent manufacturers from deducting production costs in the year paid when the goods those costs produced haven’t been sold yet. Getting UNICAP wrong means either overstating deductions (which triggers penalties on audit) or overcapitalizing costs (which means you’re paying tax earlier than you need to). Either way, the inventory line on your return deserves more attention than it usually gets.

What costs does IRC 263A force you to capitalize?

The UNICAP rules split production costs into two buckets: costs you were already capitalizing under IRC 471 (your normal inventory accounting) and additional costs that IRC 263A requires you to add on top.

Under your normal method, you’re already putting direct materials and direct labor into inventory. That part is straightforward: the steel you purchased, the wages of the welder who shaped it, and the components you bolted together all become part of the unit cost.

IRC 263A goes further. It requires you to also capitalize a portion of indirect costs that benefit production, even if those costs feel like period expenses. The list includes factory rent, utilities for the production facility, depreciation on manufacturing equipment and the factory building, property taxes and insurance on production assets, indirect labor (supervisors, quality control, maintenance crews), factory supplies, and costs related to purchasing, handling, and storage of raw materials. Repairs and maintenance on production equipment also get pulled in.

Certain costs stay deductible as period expenses regardless of UNICAP. Selling expenses, advertising, R&D expenses under IRC 174, and general corporate overhead that has no nexus to production (the CEO’s office rent in a building miles from the factory, for instance) are not required to be capitalized. Officers’ compensation is partially capitalizable only to the extent those officers perform production-related functions.

The practical effect: your ending inventory on the tax return will be higher than it would be without UNICAP, because you’ve loaded indirect costs into it. That higher inventory balance means a smaller cost of goods sold, which means higher taxable income in the year of production. You recover those costs only when the inventory sells. For manufacturers with long production cycles or growing inventory balances, the cash-flow hit from UNICAP can be significant.

How does the simplified production method work?

The simplified production method (SPM) is the most commonly used UNICAP computation approach for manufacturers, and for good reason: it avoids the complexity of tracing every indirect cost to specific production runs.

The core mechanic is an absorption ratio. You take your “additional section 263A costs” (the indirect costs that UNICAP requires you to capitalize but that you wouldn’t capitalize under your normal inventory method) and divide them by your “section 471 costs” (the costs you already include in inventory, typically direct materials and direct labor). That ratio is then multiplied by your ending inventory to determine how much additional cost to capitalize.

The formula:

Absorption Ratio = Additional Section 263A Costs / Section 471 Costs

Additional Capitalized Amount = Absorption Ratio x Ending Inventory (at section 471 cost)

The SPM can be applied using a single, combined absorption ratio or using separate ratios for different cost categories. Most small and mid-size manufacturers use the combined approach because it’s simpler and the IRS permits it. The method must be elected and applied consistently; you can’t switch methods year to year without filing Form 3115 (Application for Change in Accounting Method).

What’s the burden rate method, and when does it make sense?

The burden rate method is an alternative UNICAP approach where the manufacturer calculates a predetermined overhead rate and applies it to each unit of production. If your cost accounting system already tracks overhead allocation by job, department, or product line, the burden rate method may align more naturally with your internal books.

Under this method, you determine a rate (for example, overhead dollars per direct labor hour, or overhead as a percentage of direct material cost) and apply it to production activity during the year. The result is an overhead amount capitalized into each unit of inventory.

The burden rate method can be more precise than the SPM when a manufacturer produces significantly different products with varying overhead profiles (a custom machine shop that also does high-volume stamping, for instance). But it requires more detailed cost tracking, and the IRS expects the rate to be updated regularly to reflect actual costs. If you set a burden rate and don’t revisit it, you can end up with a significant over- or under-absorption variance, which itself must be allocated between cost of goods sold and ending inventory.

For most manufacturers under $50 million in revenue, the simplified production method is the better choice. The burden rate method tends to justify itself only when the manufacturer’s internal cost accounting is already sophisticated enough to support it without additional effort.

Does the small business exception skip UNICAP?

Yes, and this is one of the most valuable planning points in manufacturing tax. IRC 263A(i) provides a blanket exemption from UNICAP for businesses that meet the gross receipts test. For tax years beginning in 2026, the threshold is $32 million in average annual gross receipts over the three preceding tax years (this figure is inflation-adjusted annually; the original statutory threshold from the Tax Cuts and Jobs Act was $25 million).

If you qualify, you are not required to apply UNICAP at all. You account for inventory under your normal method (which can be as simple as the method you use for your financial statements, or even the cash method in some cases under IRC 471(c)). This eliminates the absorption ratio calculation, the additional capitalization layer, and the compliance burden that comes with it.

A few points that matter in practice. The test uses gross receipts, not net income or taxable income. Gross receipts include total sales, service revenue, interest, rents, and other income items before any deductions. For a manufacturer with thin margins but high revenue, this means the $32 million threshold can be breached even when profits are modest.

The test is applied at the entity level, but aggregation rules apply. If you operate through multiple entities under common control, the gross receipts of all commonly controlled entities are combined for the test. A manufacturer that splits operations across two LLCs (one for production, one for distribution) controlled by the same owners will aggregate revenue from both.

If you’re currently applying UNICAP and you’ve dropped below the threshold, or if you’ve been ignoring UNICAP and you’ve grown past it, either situation requires a change in accounting method (Form 3115). The IRS generally treats the adoption or removal of UNICAP as an automatic change, but the adjustment to taxable income (the “section 481(a) adjustment”) from switching can be spread over four years if unfavorable. Getting the timing right on this election can materially affect cash flow.

For more on how entity structure interacts with the gross receipts test and other tax planning considerations, see our guide on entity structure for manufacturers.

Should you use LIFO or FIFO for your inventory?

The choice between Last In, First Out (LIFO) and First In, First Out (FIFO) has real tax consequences, particularly during periods of rising costs.

Under FIFO, you assume the oldest inventory is sold first. When costs are rising (as they typically are for manufacturers dealing with commodity inputs), the older, cheaper units flow into cost of goods sold, leaving the newer, more expensive units in ending inventory. The result: higher ending inventory, lower cost of goods sold, and higher taxable income.

Under LIFO, the newest (and most expensive) units are assumed to sell first. During inflation, LIFO produces a higher cost of goods sold, lower ending inventory, and lower taxable income. For a manufacturer whose input costs have risen 5-10% annually, LIFO can generate meaningful, recurring tax deferral.

The tradeoff is the LIFO conformity requirement. If you use LIFO for tax purposes, you must also use LIFO for financial reporting (your audited financial statements, bank presentations, bonding applications). Many manufacturers find this unappealing because LIFO depresses reported profits and book equity, which can affect lending covenants and bonding capacity. The conformity requirement is strict: the IRS has denied LIFO elections when the taxpayer used FIFO in supplemental reports to lenders.

LIFO also adds complexity. You must maintain LIFO layers (each year’s inventory additions at that year’s cost), and if inventory quantities decrease, old LIFO layers with low historical costs get liquidated into cost of goods sold, triggering income (called “LIFO liquidation”) that can create an unexpected tax bill. Manufacturers with volatile production levels should model LIFO liquidation risk before electing.

For manufacturers with stable or growing inventory, rising input costs, and no issues with the conformity requirement, LIFO is often worth the complexity. For everyone else, FIFO’s simplicity and higher book income usually win. Either method interacts with UNICAP (the absorption ratio applies on top of whichever cost-flow method you use), and switching between them requires Form 3115. For a broader look at how inventory method fits into overall tax planning, see the guide on manufacturing tax deductions and expenses.

Can you write down inventory to market value?

The Lower of Cost or Market (LCM) method allows a manufacturer using FIFO to value inventory at the lower of its actual cost or its current market replacement cost. If the market price of your raw materials or finished goods has dropped below what you paid, LCM lets you recognize that loss before you sell the goods, reducing taxable income in the year of the write-down.

LCM is available only to FIFO taxpayers. If you use LIFO, LCM is off the table, per IRC 472. This is one of the tradeoffs of LIFO: you get the benefit of matching higher costs to revenue during inflation, but you lose the ability to write inventory down during deflation or obsolescence.

Market value for LCM purposes is generally defined as replacement cost, subject to a ceiling (net realizable value, which is the selling price minus costs to complete and dispose) and a floor (net realizable value minus a normal profit margin). If replacement cost falls between the ceiling and the floor, you use replacement cost. If it’s above the ceiling, you use the ceiling. Below the floor, you use the floor.

For subnormal goods (damaged, shopworn, or otherwise impaired), the regulations allow valuation at the selling price minus direct costs of disposal. This is a narrower category than general obsolescence and requires goods that are physically identifiable and genuinely impaired.

How do you handle obsolete or slow-moving inventory?

Inventory write-downs for obsolescence are legitimate, but the IRS scrutinizes them closely. The standard is that the goods must be “not readily salable at normal prices” or must be demonstrably unsalable. A blanket percentage write-down (writing off 10% of all inventory over 12 months old, for example) will not survive audit unless you can demonstrate, item by item or category by category, that the reserve matches actual impairment.

The strongest position is a specific identification approach: you identify particular SKUs or lots that are obsolete, document why (engineering changes, customer cancellations, superseded product lines, expiration), and write those specific items down to scrap or liquidation value. If you sell obsolete inventory to a liquidator for $0.10 on the dollar, that transaction establishes market value definitively.

Manufacturers should review inventory aging reports quarterly and document obsolescence decisions in real time, not reconstruct them at year-end. An auditor who sees a contemporaneous memo from the plant manager identifying 500 units of a discontinued part as scrap-only is far more persuaded than a year-end journal entry with no supporting detail.

The interaction between UNICAP and obsolescence write-downs also matters. If you’ve capitalized additional indirect costs into inventory under UNICAP, and that inventory is later written down, the write-down includes both the section 471 cost and the UNICAP layer. You don’t lose the UNICAP component just because the goods went obsolete.

How does inventory connect to your tax position?

Inventory method, UNICAP compliance, and cost capitalization don’t exist in a vacuum. The depreciation method you use on your equipment under section 179 or bonus depreciation affects your overall tax position and interacts with inventory costing (equipment depreciation is one of the indirect costs UNICAP requires you to capitalize, so accelerated depreciation on production equipment changes the absorption ratio). R&D credits under IRC 41 can offset some of the tax bite from UNICAP’s higher inventory values. And entity structure determines which gross receipts threshold applies and whether the small business exception is available at all, as discussed in the entity structure guide.

The bottom line: inventory accounting for manufacturers is not a bookkeeping exercise. It’s a tax planning decision that affects cash flow every year, interacts with most other tax elections, and carries audit risk if done incorrectly.

Cross-links to related guides:

• Manufacturing Tax Deductions and Expenses
• Manufacturing Equipment Depreciation and Section 179
• Manufacturing R&D Tax Credit Under IRC 41
• Manufacturing Entity Structure: LLC, S Corp, C Corp

This guide is general information, not tax advice for your specific situation. Which points apply, and how, depends on your facts.