A useful forecast separates what happened from what remains

Cost to complete is the cost you still expect to incur to finish the defined scope. It is not the same as the total job cost. To forecast a final cost, combine costs already incurred with costs still expected. Choose a status date and update the estimate when receipts, invoices, purchase orders, labor progress, or scope changes alter the picture.

Use three non-overlapping buckets

1. Actual costs incurred: costs attributable to work performed or materials received by the status date. Track whether an incurred bill is paid or unpaid separately for cash planning.
2. Open commitments: the remaining value of purchase orders, subcontract agreements, or other obligations that are not already included in actual incurred costs.
3. Remaining uncommitted forecast: your current estimate for work still needed that has not already been counted in actuals or commitments.

Keep an unpaid received invoice in the incurred-cost record if the work or materials are already attributable to the job; track its unpaid status in accounts payable or a separate cash view. Do not count that same invoice again as an open commitment. For a partially fulfilled order, include only the unincurred remainder as a commitment and place delivered work or materials in actuals. Apply one consistent policy with your bookkeeper or accountant.

Manual example

At the status date, suppose the fictional job has $23,000 incurred, $5,000 of remaining open commitments, and $8,500 of uncommitted work left to forecast.

Test a scenario without rewriting actuals

A scenario is a what-if adjustment, not a replacement for the base forecast. In this example, a documented $2,000 reduction in future uncommitted scope changes the forecast to $34,500: $23,000 actual + $5,000 commitments + $6,500 remaining. Keep the original assumptions visible so the difference can be reviewed.

Negative cost changes cannot reduce the forecast below actual incurred costs plus open commitments: $23,000 + $5,000 = $28,000. In this example, a documented $8,500 reduction in remaining work reaches that floor. A $9,000 credit would put the forecast below it, so the change-order calculator rejects that input instead of silently capping it. Review the scope, invoices, and supplier records, then reconcile any cancelled commitment with evidence before changing the underlying estimate. Do not credit work already performed, materials received, or an active obligation without a supported change.

Positive scenario adjustments can represent a revised quantity, a newly discovered task, or a contingency assumption. Label the reason and affected bucket. A scenario alone does not amend customer scope, cancel a subcontract, or release an order.

Use the cost-to-complete calculator to inspect remaining cost and the forecast total. If the change affects price, compare the change-order scenario as well. Examples are fictional; the calculations do not prescribe prices, accounting treatment, or tax advice. Ask a qualified accounting professional how to classify costs for your books.