Period costs are business expenses recorded on the income statement in the same accounting period you incur them, rather than attached to inventory and held on the balance sheet. Common examples of period costs include sales commissions, advertising, office rent, executive salaries, most research and development spending, and interest on business debt. The unifying feature is that none of these costs relate directly to making or acquiring a specific unit of inventory, so they’re expensed in the period they support instead of waiting for a sale.
Selling Expenses
Selling expenses are what a company spends to win customers and move finished product out the door. Sales commissions belong here — a percentage of revenue paid to the salespeople who close deals. So do advertising and marketing campaigns, including media placement and agency fees. Outbound shipping to get finished goods to customers is a selling expense. If you rent warehouse space to hold finished inventory before it ships, that rent is also a selling expense, because the cost sits after production ends.
General and Administrative Expenses
G&A covers the costs of keeping the corporate side of the business running. Executive compensation, meaning the CEO’s salary and the CFO’s bonus, falls here. Rent and utilities for headquarters, office supplies, general business insurance premiums, and fees paid to outside accountants or lawyers for corporate-level work like annual audits or contract review all qualify. IT infrastructure costs, including network maintenance and standard software licenses, round out the category. None of these expenses touch the production process, so none belong in inventory.
Research and Development
Under U.S. GAAP, most R&D spending is expensed immediately as a period cost. That includes salaries for research staff, the cost of materials used in experiments, and depreciation on lab equipment. The rule applies even though R&D is designed to generate future revenue. FASB’s reasoning is that the uncertainty of future benefits is too high to justify capitalizing R&D as an asset — you don’t know which projects will pay off.
Software development is the notable exception. Internal-use software costs can be capitalized once the project clears its preliminary planning stage and management commits to funding it. For software you intend to sell, capitalization begins after “technological feasibility,” which is when testing confirms the product can meet its design specifications. Anything spent before those thresholds is a period cost.
Interest Expense
Interest on business debt is a period cost because it reflects how the company is financed, not how it makes products. A monthly interest payment on a line of credit hits the income statement in the month it accrues, typically in a non-operating section below operating income.
One exception matters. When you borrow to build a long-term asset like a new factory, warehouse, or real estate development, GAAP requires you to capitalize the interest incurred during construction. That interest becomes part of the asset’s cost on the balance sheet rather than a current expense. The rule also applies to assets built for sale as discrete projects, such as ships or custom real estate. Once construction ends, ongoing interest returns to normal period-cost treatment.
How Period Costs Differ From Product Costs
The classification test is straightforward. Does the cost relate directly to making or acquiring inventory? If yes, it’s a product cost and gets capitalized as part of the inventory asset on the balance sheet. Product costs include raw materials, wages of workers on the production line, and factory overhead. They only move to the income statement as cost of goods sold once the finished product is sold.
If the cost doesn’t tie to a specific sellable unit, it’s a period cost. The matching principle drives the split: expenses should be recognized in the same period as the revenue they help generate. Since period costs support the business broadly rather than creating a specific unit of inventory, the period itself is the best match.
Misclassifying in either direction distorts both statements at once. Capitalizing an advertising expense into inventory, for example, overstates assets and understates current-period expenses. Reported profit looks higher than it should be. The error eventually reverses when the inventory sells, but by then decisions have been made on inflated numbers.
Gray Areas
Several expense categories sit close to the line, and the right answer depends on facts specific to the business.
Warehouse costs are the classic case. Rent on a warehouse storing raw materials or work-in-progress is manufacturing overhead, a product cost folded into inventory. Rent on a warehouse storing finished goods waiting to ship is a selling expense, a period cost. Same building type, different classification based on what’s inside.
Quality control follows similar logic. Inspections during manufacturing are part of production overhead and belong in inventory. Testing after goods are finished and ready to ship is arguably a selling cost. Companies with both in-process and final-stage programs need to split the costs.
Dual-use personnel create headaches. If a plant manager spends part of their time on production oversight and part on administrative tasks, the salary must be allocated between product costs and period costs. The allocation method directly changes the dollar amount sitting in inventory versus the amount expensed immediately.
Depreciation depends on the asset. Depreciation on factory equipment is a product cost, capitalized as part of manufacturing overhead. Depreciation on the corporate headquarters is a period cost. Depreciation on a delivery truck used exclusively for customer shipments is a selling expense. Same accounting concept, three different treatments.
When in doubt, the conservative approach is to treat an ambiguous cost as a period cost. Expensing immediately is more transparent and understates assets rather than overstating them.
Where Period Costs Show Up on the Income Statement
Revenue comes first. Subtract cost of goods sold to get gross profit. Period costs sit below that gross profit line, usually grouped as “Selling, General, and Administrative Expenses” or broken into “Selling Expenses” and “G&A Expenses” if the company wants more detail. Subtracting total period costs from gross profit gives operating income, the number analysts use to evaluate how well management runs the core business. Interest expense appears further down in the non-operating section, because it reflects financing choices rather than operations.
A practical consequence: because period costs hit the income statement immediately, a large one-time expense like a major advertising push or a legal settlement can significantly depress reported earnings for a single quarter. Product costs spread their impact over whatever timeframe the associated inventory takes to sell.
Tax Treatment
Book and tax treatment usually line up for period costs. Most ordinary business expenses — salaries, rent, advertising, professional fees — are deductible in the year you pay or incur them, as long as they qualify as “ordinary and necessary” expenses of running your trade or business.1Office of the Law Revision Counsel. 26 USC 162 – Trade or Business Expenses
R&D is where the two systems recently diverged and then reconverged. The Tax Cuts and Jobs Act of 2017 required businesses to capitalize and amortize domestic research expenditures over five years starting in 2022, even though GAAP still required immediate expensing. In 2025, the One Big Beautiful Bill Act introduced new Section 174A, which permanently restored immediate expensing for domestic research expenditures for tax years beginning after December 31, 2024. Foreign research spending still must be capitalized and amortized over 15 years.2Office of the Law Revision Counsel. 26 USC 174 – Amortization of Research and Experimental Expenditures
The tax code also draws a hard line between expenses and capital expenditures. Amounts paid for new buildings, permanent improvements, or anything that increases the value of a property must be capitalized and recovered through depreciation or amortization rather than deducted currently.3Office of the Law Revision Counsel. 26 USC 263 – Capital Expenditures