Fixed manufacturing costs are production overhead expenses that stay the same in total no matter how many units a factory turns out during the period. Factory rent, depreciation on production equipment, property taxes on the plant, insurance on the facility, and salaries for plant management are the standard examples. They exist to keep the ability to produce in place, so they show up whether the line runs one shift or three, and they have to be built into inventory values for both financial reporting and federal tax purposes rather than deducted as they are paid.
What Qualifies as a Fixed Manufacturing Cost
A cost is fixed when its total does not move with production volume inside the factory’s normal operating capacity. Monthly rent on the building is the clearest case. Annual property taxes on the facility, insurance premiums on the plant and equipment, and depreciation on production machinery behave the same way. So do the salaries of factory-level managers, quality control directors, and maintenance supervisors, who earn the same pay whether the line produces 2,000 units or 20,000.
That last point is where fixed manufacturing overhead separates from direct labor. Hourly production workers scale up and down with output, so their wages are variable. Supervisory compensation does not, so it lands in overhead.
IRS inventory rules track this same logic. The regulations define indirect production costs to include both fixed and variable components, and specifically list factory rent, property taxes, depreciation, insurance, utilities, and supervisory labor among the indirect costs that attach to production.
How Fixed Costs Behave Per Unit
Total fixed cost is flat. Fixed cost per unit is not. If a plant carries $500,000 of monthly fixed costs and produces 10,000 units, each unit absorbs $50. Push production to 20,000 units and the per-unit share drops to $25. This is the arithmetic behind economies of scale and the reason manufacturers push utilization toward capacity.
The spreading effect only works inside what accountants call the relevant range: the band of output the current building, equipment, and workforce can handle. Cross the ceiling and fixed costs jump to a new plateau because you need a second building, another production line, or a new shift of supervisors. Costs that hold steady across a stretch and then leap are sometimes called step-fixed.
When the Plant Runs Below Normal Capacity
The rule flips in a downturn. Under U.S. GAAP, fixed production overhead has to be allocated to inventory based on the facility’s normal capacity, not whatever output actually happened in a slow period. If your plant normally runs at 80% and drops to 40%, you cannot bury the fixed overhead tied to the unused capacity inside the value of the units you did make. That unallocated portion has to be recognized as an expense in the current period. FASB Statement No. 151 codified this so companies could not hide the cost of idle facilities on the balance sheet.1Financial Accounting Standards Board. Statement of Financial Accounting Standards No. 151
Absorption Costing vs. Variable Costing
How fixed overhead moves through the books depends on who is reading them.
For external financial statements, both U.S. GAAP and IFRS require absorption costing. Every unit of inventory carries its share of fixed manufacturing overhead alongside direct materials, direct labor, and variable overhead. The fixed overhead sits on the balance sheet inside inventory value until the goods sell, then moves to the income statement as cost of goods sold. IAS 2 requires the allocation to be based on normal capacity,2IFRS Foundation. IAS 2 Inventories and ASC 330 under U.S. GAAP follows the same principle.1Financial Accounting Standards Board. Statement of Financial Accounting Standards No. 151
One side effect trips people up. When a company builds inventory faster than it sells, absorption costing defers some of the current period’s fixed overhead onto the balance sheet instead of expensing it. Reported profit looks stronger. When inventory levels fall, the reverse happens. Manufacturing margins can swing between periods for reasons that have nothing to do with pricing or efficiency.
Variable costing treats fixed manufacturing overhead as a period expense in full, no matter what was produced or sold. Only variable production costs attach to each unit. This method is not allowed for external financial statements or IRS reporting, but plenty of manufacturers keep it running internally because it isolates contribution margin. When you are pricing a special order or weighing whether to drop a product line, variable costing strips out allocated fixed overhead and shows the incremental economics more directly.
Tax Treatment Under Section 263A
For federal income tax, manufacturers work under a separate set of capitalization rules. Section 263A of the Internal Revenue Code, known as the Uniform Capitalization rules or UNICAP, requires producers to capitalize direct costs and an allocable share of indirect costs into inventory rather than deducting them as incurred.3Office of the Law Revision Counsel. 26 U.S. Code 263A – Capitalization and Inclusion in Inventory Costs
The list of indirect costs covered by UNICAP catches most fixed manufacturing expenses: factory rent, depreciation on production equipment and buildings, property taxes, insurance on plant and machinery, utilities, quality control and inspection costs, repairs and maintenance, and supervisory compensation.4eCFR. 26 CFR 1.263A-1 Uniform Capitalization of Costs None of these can be deducted in the year they are paid. They stay embedded in inventory until the goods sell, then reduce taxable income through cost of goods sold.
Section 263A is often broader than GAAP absorption costing, especially for administrative and service costs that benefit production. A cost that GAAP allows as a period expense can still be a required capitalization under UNICAP, so the tax computation of inventory rarely matches the book number line for line.
The Small Business Exemption
Not every manufacturer has to comply. Section 263A exempts businesses that meet the gross receipts test under Section 448(c), which uses a base threshold of $25 million in average annual gross receipts over the prior three tax years, adjusted for inflation each year and published by the IRS in an annual revenue procedure.3Office of the Law Revision Counsel. 26 U.S. Code 263A – Capitalization and Inclusion in Inventory Costs Manufacturers below the threshold can use simpler inventory methods without capitalizing the full range of indirect costs UNICAP demands. Tax shelters do not qualify regardless of gross receipts.
Depreciation on Production Equipment and Buildings
Depreciation is typically the largest fixed manufacturing cost by dollar amount, and the tax code offers several ways to pull the deduction forward.
MACRS Recovery Periods
Under the Modified Accelerated Cost Recovery System, most general-purpose manufacturing machinery has a 7-year recovery period. Specific industries have their own class lives, with dedicated categories for areas like semiconductor manufacturing, food processing, and paper production listed in the asset class tables in IRS Publication 946.5Internal Revenue Service. Publication 946 – How To Depreciate Property Factory buildings themselves depreciate over 39 years as nonresidential real property.
Section 179 Expensing
Section 179 lets you deduct the full cost of qualifying equipment in the year it is placed in service. For tax years beginning in 2026, the maximum deduction is $2,560,000, phasing out dollar-for-dollar once total equipment purchases exceed $4,090,000 in the year.5Internal Revenue Service. Publication 946 – How To Depreciate Property The deduction cannot exceed taxable income from active business operations, so it cannot create or increase a net operating loss.
100% Bonus Depreciation
The One, Big, Beautiful Bill Act restored 100% first-year bonus depreciation for qualified property acquired and placed in service after January 19, 2025.6Internal Revenue Service. One, Big, Beautiful Bill Provisions A manufacturer buying new production equipment in 2026 can deduct the entire cost in year one. Unlike Section 179, bonus depreciation has no dollar cap and can generate a net operating loss. Taxpayers may elect a reduced 40% first-year deduction instead of the full 100% for property placed in service during the first tax year ending after January 19, 2025.7Internal Revenue Service. Treasury, IRS Issue Guidance on the Additional First Year Depreciation Deduction Amended as Part of the One, Big, Beautiful Bill
Book depreciation does not follow these accelerated tax deductions. On the financial statements, the equipment continues to depreciate over its useful life, and the gap between tax and book depreciation becomes a deferred tax liability that reverses over the remaining life of the asset.
Where Manufacturers Get the Classification Wrong
The costs that cause the most trouble are the ones with mixed behavior. Factory utilities often have a fixed base charge plus a variable usage component. Maintenance contracts frequently combine a flat monthly fee with per-call charges. Treating either as purely variable understates the overhead base, and treating it as purely fixed distorts how per-unit costs move with production.
The tax exposure is more concrete. IRS inventory regulations require manufacturers to distinguish direct and indirect production costs properly and include all applicable indirect costs in inventory.8eCFR. 26 CFR 1.471-11 – Inventories of Manufacturers Deducting a capitalizable fixed cost as a period expense pulls the deduction forward improperly, which can produce adjustments, interest, and penalties on audit. The costs sitting on the fixed-variable boundary are worth flagging when you set up the general ledger, not when the examiner asks.