Cost Accounting Standards (CAS) for Government Contractors: Coverage, Thresholds, and What They Require

A different rulebook than the one about allowability

Government contractors quickly learn that ordinary accounting rules are not the whole story. Two federal frameworks sit on top of generally accepted accounting principles, and it is easy to blur them together. The first, FAR Part 31, governs allowability — whether a given cost can be charged to the government at all. The second is the Cost Accounting Standards, or CAS, and it governs something different: the measurement, assignment to accounting periods, and allocation of costs. Put plainly, FAR 31 asks "can you charge this cost?" and CAS asks "how, and in which period, and to which contracts, do you charge your costs — and do you do it consistently every time?"

CAS is administered by the Cost Accounting Standards Board and codified separately from the FAR (in its own part of the federal acquisition regulations). It exists because two contractors could each follow GAAP and still account for the same cost in wildly different ways, making it impossible for the government to compare bids or trust that a cost-reimbursable contract is being billed the way it was priced. CAS closes that gap by imposing uniformity and consistency. This article walks through who is actually covered, the two tiers of coverage, and what the standards require — because whether they apply to you can change with a single award. (This is general educational information about government-contract cost accounting, not accounting, legal, or contracting advice; thresholds and rules are periodically revised, so confirm current figures and applicability with a qualified contract accountant.)

Most small contractors are exempt — but not permanently

Here is the reassuring part for the typical small business reading this: there are broad exemptions from CAS, and small businesses are squarely inside them. Among the categories generally exempt from CAS are:

• Contracts and subcontracts awarded to small businesses — a blanket exemption regardless of contract size.
• Firm-fixed-price contracts awarded on the basis of adequate price competition without the submission of certified cost or pricing data.
• Contracts for commercial products and services acquired under commercial-item procedures.
• Sealed-bid contracts.
• Negotiated contracts and subcontracts below the applicable trigger dollar threshold, provided the business unit is not already performing a CAS-covered award at or above that threshold.
• Contracts performed entirely outside the United States.

So a small business winning fixed-price, competitively awarded, or commercial-item work is typically not carrying CAS obligations. The reason to understand CAS anyway is that none of those exemptions are guaranteed to last. Win a large enough cost-type award, grow past your small-business size standard, or take a subcontract under a covered prime, and CAS can attach. Contractors who wait until that happens to learn the standards tend to discover their accounting system was never built to comply.

The two tiers: modified and full coverage

When CAS does apply, it applies at one of two levels, and the difference is large.

Modified coverage is the lighter tier. It applies to a covered contract below the full-coverage threshold, awarded to a business unit that has not crossed into full coverage. Under modified coverage, only four of the standards apply:

• CAS 401 — Consistency in estimating, accumulating, and reporting costs. In short: bid the way you book, and book the way you bid. The practices you use to estimate a proposal must match the practices you use to accumulate and report actual costs.
• CAS 402 — Consistency in allocating costs incurred for the same purpose. A cost incurred for the same purpose, in like circumstances, must be treated either as a direct cost or as an indirect cost — never charged one way here and the other way there. This is the core discipline behind classifying direct versus indirect costs consistently.
• CAS 405 — Accounting for unallowable costs. You must identify and segregate unallowable costs so they are excluded from any billing, claim, or proposal — the accounting counterpart to knowing your FAR Part 31 unallowables.
• CAS 406 — Cost accounting period. Use a consistent cost accounting period — generally your fiscal year — for accumulating costs and computing indirect rates.

These four are, not coincidentally, the disciplines that even non-CAS-covered contractors effectively have to demonstrate to show an adequate accounting system. They are the foundation everything else rests on.

Full coverage is the heavy tier: all nineteen standards apply. Full coverage is triggered when a business unit receives a single CAS-covered award at or above the full-coverage threshold, or when it received net CAS-covered awards at or above that threshold in its immediately preceding cost accounting period. As a long-standing benchmark, the trigger amount that first pulls a contractor into coverage has been set at several million dollars per contract, while the full-coverage threshold sits substantially higher — historically on the order of fifty million dollars in a single award or in net awards for the prior period. These figures are adjusted over time, so treat them as the shape of the rule rather than exact current numbers, and verify the amounts in force when it matters.

What the full set of standards covers

The nineteen standards (numbered CAS 401 through 420, with one number unused) reach into nearly every corner of how a contractor accounts for cost. Beyond the four core consistency standards above, they govern things like: how a home office allocates expenses to its segments; how tangible capital assets are capitalized and depreciated; how standard costs for material and labor are used; how compensated personal absence (paid time off) and deferred compensation are accounted for; how general and administrative expense is allocated to final cost objectives; how material, pension, insurance, and independent research and development costs are handled; and the treatment of facilities-capital cost of money. Each standard exists to remove a specific way two contractors could otherwise account for the same thing differently.

You do not need to memorize all nineteen to grasp the point: CAS reaches past whether a cost is allowable and dictates how it is measured, when it is recognized, and how it is spread across contracts — with the goal that a dollar of cost is accounted for the same way no matter which contract it touches.

The Disclosure Statement, and the cost of getting it wrong

A full-coverage contractor generally must file a Disclosure Statement — a formal document describing, in detail, the cost accounting practices it uses: how it classifies direct and indirect costs, how it builds its indirect pools and bases, its depreciation and capitalization policies, and so on. Once disclosed, those practices are not just described — they are binding. The contractor must follow them consistently, and cannot quietly change how it accounts for costs.

That binding quality is where the real teeth of CAS live. If a covered contractor changes a cost accounting practice, or is found to be noncompliant with a standard or with its own disclosed practices, the government can require a cost impact analysis and recover any increased costs the change or noncompliance caused it to pay. This is why CAS is not a paperwork exercise: the standards, once they apply, constrain how you are allowed to run your accounting, and deviating from them carries a real financial adjustment. It connects directly to the year-end reckoning of an incurred cost submission and to the provisional billing rates you invoice with — all of which have to rest on consistent, disclosed practices.

What to actually take from this

For most small contractors, the practical message is a two-parter. First, you are probably exempt today — small-business, commercial-item, and competitively-awarded fixed-price work keeps CAS off your back. Second, build as if it is coming anyway. The four modified-coverage disciplines — estimate the way you accumulate, treat like costs alike, segregate unallowables, and use a consistent accounting period — are exactly the habits that make your books credible to the government whether or not CAS technically applies. A chart of accounts that cleanly segregates direct costs, indirect pools, and unallowables is the same foundation you would need if a large cost-type award pulled you into coverage overnight.

CAS, in one line: it is not about whether you can charge a cost, but about charging every cost the same consistent way, in the same period, allocated the same manner, every time — so the government can trust that what you bid is what you bill.

Hosting Books structures direct costs, indirect pools, and unallowable costs into a consistent chart of accounts and holds those practices steady across periods, so a contractor's books stay estimate-to-actual consistent whether it is demonstrating an adequate accounting system today or preparing for CAS coverage tomorrow.

This article is general educational information about government-contract cost accounting concepts and is not accounting, legal, or contracting advice for your specific situation. CAS coverage rules and dollar thresholds are set by regulation and revised over time — confirm the current requirements and figures that apply to your business with a qualified contract accountant or CPA.