Cost-plus construction audit: test reimbursable costs

Build a cost-treatment register before reviewing charges

Extract the agreement's reimbursable categories, exclusions, allocation rules, fee basis and documentation rights. Include amendments and relevant written decisions. Assign a reviewer to unresolved interpretations rather than allowing each invoice preparer to apply a different rule.

For each category, record whether the contract uses actual costs, an agreed rate, a cap or another method. Those methods require different evidence. A scheduled equipment rate is not necessarily tested against a rental invoice; an actual-cost reimbursement is not established by a schedule alone. Preserve the contractual basis beside the test so the reviewer can see why a charge was accepted.

Trace charges through source records and allocation

Select a transaction and trace it from invoice or labor record to the job-cost ledger and the owner's reimbursement request. Check dates, location, cost category, tax, credits and any allocation to other projects. Confirm that the source value was not included in a separate package or fee.

Use a consistent allocation basis where the agreement requires shared costs to be allocated. Record the population and units behind the allocation. A percentage without a denominator is not reproducible. Where evidence is inaccessible under the actual agreement, report a coverage limitation instead of pretending the cost passed.

Worked example: the fee can amplify a cost exception

A fictional monthly reimbursement contains $40,000 of eligible direct costs and $3,000 of office overhead. Assume this agreement excludes that overhead from reimbursement and applies a 6% fee to eligible direct costs only. The submitted $43,000 base plus $2,580 fee totals $45,580.

Under those assumptions, the reviewed amount is $40,000 plus $2,400, or $42,400. The proposed difference is $3,180: $3,000 of excluded cost plus $180 of fee. A different agreement could include the overhead or use another fee basis. Cite the actual clause before adopting the calculation, and distinguish a proposed reduction from an agreed or posted adjustment.

Review returns, rebates and later corrections

A cost review is incomplete if it stops at the first invoice. Match subsequent credit memos, returned materials, discounts and corrections to the original reimbursed cost. Confirm the contractual treatment and the period in which the adjustment belongs.

FAR 31.201-5 addresses applicable credits in its federal cost-principle context. It is a useful reference for that context, not a universal clause for private construction. For a private owner, use the executed agreement's definitions and applicable requirements. Keep unresolved credit entitlement visible for the responsible commercial reviewer.

Sources: FAR 31.201-5: Credits (federal context, subject to applicability)

Deliver a decision register rather than an unsupported savings total

Show the sampled cost, governing basis, evidence received, reviewed amount and contractor response. Distinguish unsupported costs awaiting records from costs the authorized team has agreed are excluded. Record clean items as well; they demonstrate what the review actually covered.

For Buildalytic, start by discussing how to collect missing cost support and route exceptions around the current accounting system. Any audit calculation, rate library or custom integration needs a defined scope and acceptance test. A recurring engagement should specify reviewed contracts, periods and human responsibilities. The measurable result is confirmed treatment and review effort, with financial benefits recorded only when independently validated.

Sources: Buildalytic: current custom-workflow scope