Indirect cost pools are groupings of shared business expenses that a government contractor cannot trace to a single contract, allocated across all work using a rate tied to a logical base. Most contractors build three primary pools — fringe benefits, overhead, and general and administrative — and calculate a rate for each by dividing the pool total by an allocation base such as direct labor dollars or total cost input. The Federal Acquisition Regulation sets the rules for how those pools are structured, how the costs inside them qualify, and how the resulting rates get billed and audited.
The Two Consistency Rules That Shape Every Pool
Before deciding which pools to build, a contractor has to satisfy two consistency requirements. Both are audit magnets.
The first is homogeneity. FAR 31.203 requires contractors to accumulate indirect costs in groupings that let the allocation base distribute costs based on the benefits each project receives. Costs inside a pool must share a logical relationship to the projects that absorb them. Facility costs — rent, utilities, building maintenance — belong together because they all scale with physical space. Dropping corporate legal fees into that same pool breaks the logic. The regulation also builds in a pragmatism check: when a simpler grouping produces substantially the same result, extra sub-pools aren’t required.1eCFR. 48 CFR 31.203 – Indirect Costs
The second is the direct-versus-indirect rule. FAR 31.202 states that if a cost has been charged directly to any contract, other costs incurred for the same purpose in similar circumstances cannot be included in an indirect pool allocated to that or any other contract. Charging travel directly to Contract A while routing similar travel through overhead on Contract B is the textbook violation. A narrow exception lets minor amounts be treated as indirect if the practice is applied consistently and produces substantially the same result as direct charging.2Acquisition.gov. FAR 31.202 – Direct Costs
Contractors above certain dollar thresholds face additional Cost Accounting Standards requirements. CAS 401 requires that the practices used to estimate costs in a proposal match the practices used to accumulate and report actual costs during performance, so the pool structure proposed at bid time has to match the structure used once work begins. CAS 402 reinforces the direct-versus-indirect rule for costs incurred for the same purpose in like circumstances.3Acquisition.gov. Part 9904 – Cost Accounting Standards Even contractors exempt from CAS must follow the FAR consistency rules.
The Standard Pools Contractors Build
Most contractors organize indirect costs into three to five pools. The exact structure depends on size and operations, but auditors expect a clear rationale for every grouping.
Fringe Benefits
The fringe pool captures the employer-paid costs of employing personnel beyond base wages. It typically includes the employer’s share of Social Security and Medicare taxes, totaling 7.65% of covered wages,4Internal Revenue Service. Topic No. 751, Social Security and Medicare Withholding Rates plus health insurance premiums, workers’ compensation, employer 401(k) contributions, and paid leave accruals. Grouping these together produces a single fringe rate applied to all labor hours across every project.
Overhead
Overhead covers the cost of running a specific operational function — a manufacturing floor, an engineering department. Supervisor salaries for managers overseeing multiple projects, shop supplies, equipment depreciation, and rent and utilities for production space all fit here. The common thread is support for the environment where employees perform billable work, even though no single project caused the cost.
General and Administrative
The G&A pool captures company-wide management costs that benefit the entire business: executive compensation, accounting and HR, corporate insurance, general legal fees. Because G&A supports every function, it’s usually allocated over total cost input rather than labor alone.
IR&D and B&P
Independent research and development covers research not sponsored by a specific contract; bid and proposal costs cover preparing proposals for future work. Both are generally allowable as indirect expenses when reasonable and allocable. For contractors not subject to full CAS requirements, IR&D and B&P must be allocated using the same base as the G&A pool of the profit center where they were incurred.5eCFR. 48 CFR 31.205-18 – Independent Research and Development and Bid and Proposal Costs
Facilities Capital Cost of Money
Facilities capital cost of money is an imputed cost representing the opportunity cost of capital invested in facilities and equipment. It isn’t actual interest expense; actual interest is unallowable. It’s a calculated figure recognized as allowable under FAR 31.205-10 when the contractor identifies it separately in cost proposals and measures it under CAS 9904.414.6Acquisition.gov. FAR 31.205-10 – Cost of Money Capital-intensive contractors often claim it; others skip it.
Choosing an Allocation Base
The allocation base is the denominator in the rate calculation. Picking a base that doesn’t reflect how the pool’s costs are actually consumed distorts what each contract pays.
- Direct labor dollars — total gross wages paid to employees working directly on contracts. Works when pooled costs rise and fall with project payroll.
- Direct labor hours — total hours worked directly on contracts. Better than labor dollars when wage rates vary widely, since an hour of work draws roughly the same overhead regardless of pay rate.
- Total cost input — the sum of direct labor, materials, subcontracts, and other direct costs. The standard choice for G&A because corporate management costs support the full volume of business activity, not just labor.
A mismatched base creates inequitable results. If overhead is allocated on labor dollars but actually tracks with machine usage, machine-heavy contracts are undercharged while labor-heavy contracts absorb more than their share.
Some organizations also run intermediate service pools — IT support, motor pools, reprographics — that benefit multiple primary pools rather than flowing to contracts directly. These allocate first to the primary pools based on usage metrics like help desk tickets, miles driven, or copies produced, and only then do the primary pools push out to contracts.
Keeping Unallowable Costs Out
FAR 31.201-6 requires contractors to identify and segregate unallowable costs from their indirect pools.7eCFR. 48 CFR 31.201-6 – Accounting for Unallowable Costs Common unallowables include entertainment, alcohol, fines and penalties, lobbying costs, and donations. The chart of accounts should segregate these clearly so they can’t drift into a rate proposal.
The stakes are steep. Under FAR 42.709, claiming an expressly unallowable cost triggers a penalty equal to the full disallowed amount allocated to covered contracts, plus interest on any portion already paid. If the contractor knew the cost was unallowable before submitting the proposal because it had been previously determined unallowable for that contractor, the penalty doubles to twice the disallowed amount.8GovInfo. 48 CFR 42.709-2 – General These penalties apply whether or not the government actually paid the costs, and they stack on top of any administrative, civil, or criminal penalties.
Calculating the Rate
The math is straightforward. Divide the pool total by the total value of the allocation base and express the result as a percentage. An overhead pool of $100,000 divided by a $500,000 direct labor base produces a 20% overhead rate. A fringe pool of $76,500 divided by the same $500,000 base produces a 15.3% fringe rate.
On each invoice, the contractor applies every applicable rate to its relevant base. A project charging $10,000 in direct labor picks up $2,000 of overhead at 20% and $1,530 of fringe at 15.3%, plus whatever G&A rate applies to the broader cost total. Each rate layer recovers a different category of shared expense, and together they distribute operating costs across the contract portfolio.
Provisional Rates and the Year-End True-Up
Contractors can’t wait until year-end to bill for indirect costs, so provisional billing rates keep cash flowing during the fiscal year. The contracting officer or cognizant auditor sets these rates before the year begins, aiming to approximate what the final rates will be after unallowable costs are stripped out. They’re typically built from recent audit results, the prior year’s actual indirect experience, or the coming year’s budget adjusted for expected unallowables. When the contract volume doesn’t justify a detailed proposal, the contracting officer can just adjust last year’s numbers for nonrecurring and unallowable items. Either party can request a revision during the year if actuals are running significantly high or low; if the parties can’t agree, the contracting officer sets the rate unilaterally.9Acquisition.gov. FAR 42.704 – Billing Rates
After each fiscal year ends, the contractor has six months to submit a final indirect cost rate proposal, commonly called an incurred cost submission.10Acquisition.GOV. FAR 52.216-7 – Allowable Cost and Payment Extensions require written approval from the contracting officer and are granted only for exceptional circumstances. If a submission runs six months delinquent, DCAA recommends that the contracting officer apply a decrement factor and make a unilateral rate determination, typically at a level unfavorable to the contractor.11Defense Contract Audit Agency. Incurred Cost Submissions Once final rates are negotiated, the contractor adjusts prior billings against the settled rates. That reconciliation is where the contractor either collects more or writes a check back to the government.
What DCAA Looks At
The Defense Contract Audit Agency is the primary auditor of indirect rates for Department of Defense contractors and often handles audits for other federal agencies.
Audits begin with an adequacy review: does the incurred cost submission comply with the regulations and contain enough detail to be audited?12Defense Contract Audit Agency. Intro to DCAA and Audit Process Inadequate submissions get kicked back while the delinquency clock keeps running. An adequate submission moves to an entrance conference where the auditor lays out purpose, scope, and expected duration, followed by walkthroughs of the contractor’s cost accumulation processes.
From there, auditors visit the contractor’s site, request supporting documentation, and hold interim discussions on questions and preliminary findings. The audit closes with an exit conference where the contractor can respond before the final report goes to the contracting officer.12Defense Contract Audit Agency. Intro to DCAA and Audit Process Clean records and a chart of accounts that maps cleanly to the pool structure make the whole process faster.
A Note on Federal Grant Recipients
Everything above applies to contractors operating under the FAR. Organizations receiving federal grants or cooperative agreements operate under 2 CFR Part 200, which offers a simpler option. Recipients and subrecipients that have never had a federally negotiated indirect cost rate may elect a de minimis rate of up to 15% of modified total direct costs instead of building a full rate structure. The de minimis rate requires no justifying documentation and can continue indefinitely, but it cannot be applied to cost-reimbursement contracts issued directly by the federal government under the FAR, and once elected it must be used for all federal awards until the organization switches to a negotiated rate.13eCFR. 2 CFR 200.414 – Indirect Costs For contractors whose true indirect costs exceed 15%, a negotiated rate recovers more.