Knowledge · Finance
Forecast final cost in construction,
the whole job's number.
Forecast final cost is the best current estimate of what the whole job will have cost when it is finished, cost to date plus commitments plus cost to complete. This reference covers how it is built, how it differs from cost to complete, why the movement in forecast final margin is the number that matters, and why it is the denominator that drives WIP accuracy.
01 / Overview
What forecast final cost is
Forecast final cost is the best current estimate of what the whole job will have cost when it is finished. It is sometimes called estimated final cost, forecast cost at completion or cost at completion, and it is the whole-of-job number at the centre of construction WIP reporting. Three parts build it up, cost to date coded to the job, plus committed costs not yet invoiced, plus the cost to complete on work not yet committed.
The boundary with cost to complete is the one to get right, because the two are constantly confused. Cost to complete is only the remaining piece, the forecast of what it will still cost to finish from today. Forecast final cost is the whole build, the part already spent and the part still to come, in one figure. Cost to complete is the main input to forecast final cost, and this reference links it rather than re-explaining it, because the forecasting judgement in that remaining piece is a subject in its own right.
Why it matters
The estimate decided what the job should cost. Forecast final cost is the running answer to what it will cost, and set against forecast final revenue it produces the forecast final margin, the only version of the profit answer available while the outcome can still change. A job's profitability is not discovered at close-out, it is decided across the build, and a current forecast final cost surfaces an eroding margin while it is still a decision rather than a fact. The day-to-day tracking that feeds it is covered in the builder cost tracking guide.
02 / The lifecycle
Where forecast final cost sits in a residential job
Forecast final cost begins where the estimate ends. On a win the priced scope becomes the job budget, and from that day the budget is the baseline the forecast measures against. Each cost review rolls cost to date, committed and cost to complete by cost code into the forecast final cost, which makes it the forward-looking whole-of-job figure that broader cost control is really steering. The part of that figure a builder can still influence is the cost to complete on the uncommitted lines, so that is where a review spends its attention.
Downstream, forecast final cost is a load-bearing input. Work-in-progress reporting rests on it directly, because the percentage complete used in the WIP formula is cost to date over forecast final cost, so the accuracy of this number drives WIP accuracy. The same figure anchors the cash flow view, since the remaining costs inside it are the payments still to go out. When forecast final margin erodes review by review, that pattern is profit fade, and the forecast is where it shows up first if the number is kept honest.
03 / Process workflow
Building the forecast, step by step
Eight steps, from the fixed floor of cost to date to feeding the number downstream. The third step, pricing the uncommitted work honestly, is where the whole forecast is either true or decorative.
- 01
Take the cost to date as given
Everything invoiced and coded to the job is the fixed floor of the number. Nothing done at the review changes it. Its only job in the forecast is to be current and correctly coded, so the rest of the build can measure against a real starting point rather than a stale one.
- 02
Add the commitments not yet invoiced
For every line with a purchase order or subcontract in place, add the committed value plus any known variances, back-charges and quantity adjustments. These lines are largely settled, so the work here is confirming that what is already known has been recorded, not forecasting it fresh.
- 03
Add the cost to complete on uncommitted work
For every line not yet ordered, add what the work would actually cost to buy today at current quotes and current rates, against what the drawings now show. This is the forecasting piece, and it is the only part of the number where judgement, and therefore optimism, lives.
- 04
Roll up the forecast final cost
Cost to date plus commitments not yet invoiced plus cost to complete, summed by cost code, is the forecast final cost, the best current estimate of what the whole job will have cost when it is finished. It is a whole-of-job number, not a remaining-work number.
- 05
Set the forecast final revenue beside it
Contract value plus approved variations is the forecast final revenue. Approved variations have to flow into both sides at once, the cost of the changed work and the revenue for it, or the margin compares a new job against an old plan and reads wrong in one direction.
- 06
Read the forecast final margin
Forecast final revenue minus forecast final cost is the forecast final margin, the current answer to whether the job will make money. Held against the margin the job was won on, it says whether the outcome is still the one that was priced.
- 07
Explain the movement since the last review
Compare this margin to the last one and give every material movement a reason, an approved variation, a rate movement, a scope gap found, a contingency draw. The movement, not the level, is the early-warning signal, and a movement without a reason cannot be trusted or learned from.
- 08
Feed the number downstream
The forecast final cost becomes the denominator of the WIP percentage-complete calculation and the spine of the cash flow view. A forecast that is wrong quietly makes both of those wrong with it, which is why the honesty of this one number carries so far.
04 / Key mechanics
The build-up of the number, part by part
Forecast final cost and the margin that sits on it are assembled from these parts. Getting the boundaries between them right is what separates a forecast from a guess with a total on the bottom.
Cost to date
Actual costs invoiced and coded to the job so far. This is the fixed part of the forecast final cost, the part already spent and beyond changing. Its contribution to accuracy is being current and correctly coded, nothing more.
Commitments not yet invoiced
Purchase orders and subcontracts in place where the invoice has not yet arrived, at committed value plus known variances. High certainty, and one of the three inputs to the whole number rather than the whole number itself.
Cost to complete
The forecast of remaining spend on work not yet committed, priced at what it would cost to buy today. This is the judgement piece and the whole subject of its own reference. It is a component of forecast final cost, never a synonym for it.
Approved variations, both sides
Signed changes to scope adjust the forecast final cost and the forecast final revenue together. Recorded on one side only, the margin moves for a reason that is half real, which is worse than not recording it at all.
Forecast final revenue
Contract value plus approved variations, the whole-of-job revenue side. Pending variations and unpriced instructions are carried visibly as revenue risk until they are signed, not quietly assumed into the number.
Forecast final margin
Forecast final revenue minus forecast final cost. The single number that says whether the job will make money while that can still change, and the number whose movement between reviews is the one that matters.
Forecast final margin, and why the movement is the number
Forecast final revenue is contract value plus approved variations. Forecast final margin is that revenue minus forecast final cost, and it is the single figure that says whether the job will make money. The level of the margin tells you whether the job is in front today. The movement in the margin, between one review and the next, tells you which way the job is heading, and that is the earlier and more useful signal. A margin still positive but drifting two points the wrong way in a month is a job developing a problem you can still act on.
This is also why forecast final cost is the denominator of the WIP percentage-complete calculation. Percentage complete on a cost basis is cost to date over forecast final cost, so understating the forecast final cost overstates the percentage complete, and the WIP position reports more of the job done than has been done. The WIP formula inherits the accuracy of this number exactly, which is why keeping the forecast honest is not a bookkeeping nicety but the thing that keeps the whole reporting chain true. How a WIP position translates into recognised revenue is an accounting treatment to settle with the builder's accountant.
Cadence, when the forecast must move
Common practice among builders who run this well is monthly at minimum, refreshed at every progress claim, and reworked on every major variation. The claim link is the non-negotiable one, because a claim asserts a percentage of the job is complete and that assertion is only as good as the forecast final cost under it. Approved variations flow into both sides at once, cost and revenue, and pending variations are carried as visible risk (the mechanics of that are covered in variations). In a rising-cost market the forecast decays faster, so the cadence that was comfortable in a flat market is usually too slow.
05 / Best practice
How experienced builders keep the forecast honest
The operator's observation is that forecast final cost is where optimism hides in plain sight. Leaving an uncommitted line at its budget value is not a neutral act. It silently forecasts that the rest of the job will behave better than the part already built has, which is the one assumption the evidence on the page usually contradicts. The discipline that catches it is unglamorous, forcing every remaining line to answer why it still equals budget, with a current quote, a current rate or a stated reason, and treating silence as an unanswered question rather than a pass.
The same operators treat the forecast as a teaching instrument. A builder learns more from three honest forecast final cost reviews on a live job than from any close-out post-mortem, because the review happens while the causes are still visible and the decisions still open, and the post-mortem happens when both are gone. The pattern across reviews is the diagnostic, which trades drift, which lines stayed open too late, how often a pending variation sat unpriced while the work proceeded. The point is not the number itself but what the movement in it teaches, in the present tense, while the job can still be steered.
Where software fits the workflow
Traditionally the forecast is a spreadsheet rebuilt each month from the ledger, a stack of invoices and memory, which is why it so often is not rebuilt at all. In VIABUILD, cost tracking holds budget, committed, actual and forecast against each cost code as orders are raised, and Oryn™ reads and codes supplier invoices as they arrive, so cost to date and the committed lines are already current when the review starts. The review then spends its time where the judgement lives, on the cost to complete for the uncommitted lines, and the forecast final cost and its margin update as a live view rather than a month-end reconstruction.
06 / Australian considerations
Forecast final cost in the Australian environment
Forecast final cost is an internal management discipline, not a legislated one, but it operates inside a regulated contract environment and, at the moment, a hard market. The points below are labelled by evidence class; figures and requirements change, so confirm the current source before relying on any of them.
- Common practice. WIP schedules built on forecast final cost are what accountants, financiers and home warranty insurance eligibility assessments commonly ask a builder to produce, and the quality of the forecast underneath decides whether those schedules survive scrutiny. How forecast final cost flows into recognised revenue is an accounting treatment; take that question to the builder's accountant rather than to a web page.
- Legislation. The variations that move a forecast on both sides are regulated. Each state and territory's domestic building contract legislation sets rules for how variations to residential work are documented, priced and approved, and the rules differ by jurisdiction. A forecast carrying work that proceeded without an approved variation is carrying a compliance question as well as a cost one, so confirm the current rules for your state.
- Professional recommendation. Industry commentary through the current contraction has been consistent that cashflow discipline matters more in a downturn, not less, and that builders who keep cost to complete, and therefore forecast final cost, current sit in a materially different position to those who do not. The pattern behind that is stable, building businesses rarely fail for lack of work, they fail on cash and on jobs whose losses were found late.
- Statistics. Published figures for the current cycle have shown a record number of Australian construction companies entering external administration, with construction topping the industry count for insolvencies. Insolvency figures move each reporting period, so confirm the current numbers against ASIC's published statistics rather than quoting a figure from memory. The context is drawn out in the cost control reference.
07 / Common mistakes
Where forecast final cost actually goes wrong
Each of these leaves the forecast looking authoritative while quietly disconnecting it from the job, and none of them requires anyone to lie. Leaving a line at budget does the damage on its own.
Uncommitted lines left at budget
The cost to complete piece defaults to the budget figure, so the whole forecast silently assumes the rest of the job will behave better than the part already built has. Each line looks fine, the total looks fine, and the overrun stays invisible until the orders are raised.
Confusing the whole with the remaining piece
Cost to complete is only the forecast of remaining spend. Forecast final cost is the whole-of-job number that contains it. Treating the two as the same understates the job by the entire cost to date and produces a margin that is nonsense.
Variations recorded on one side only
An approved variation added to the cost but not the revenue, or the reverse, moves the forecast final margin for a reason that is only half true. The margin looks worse or better than the job actually is, and the error compounds every review.
The forecast never revisited
A forecast final cost produced once and rolled forward untouched is a photograph, not a forecast. The margin that erodes rarely erodes in one event, it erodes slowly inside a number nobody re-examined between claims.
Watching the level, not the movement
A forecast final margin that is still positive can be a margin that has moved three points the wrong way in a month. The level says whether the job is in front today, the movement says which way it is heading, and the movement is the warning.
A WIP built on an optimistic denominator
Percentage complete is cost to date over forecast final cost. An optimistic forecast final cost inflates the percentage, so the WIP position reports more work done than the job has done, and an over-billed position reads as healthy.
08 / Practical example
A worked forecast final cost at frame stage
Illustrative only, not a benchmark. A custom home is contracted at $850,000 with two approved variations totalling $30,000, so forecast final revenue is $880,000. The budgeted cost is $760,000. At frame stage, cost to date sits at $320,000 and commitments not yet invoiced at $240,000. The uncommitted lines total $180,000 at budget, so the lazy forecast writes $180,000 as the cost to complete, reports a forecast final cost of $740,000, a forecast final margin of $140,000, and everyone relaxes.
The honest walk tells it differently. The painting quote has come in $6,000 over allowance, the cabinetry package is not yet ordered and current quotes run $8,000 over, the landscaping market has moved about $4,000 since pricing, and an unpriced site instruction for extra drainage is carried as a further $3,000 exposure. The cost to complete becomes $201,000, the forecast final cost becomes $761,000, and the forecast final margin falls to $119,000. The margin has moved roughly $21,000 the wrong way since the last review. At frame stage that movement is a set of decisions, price the drainage as a variation, requote the cabinetry, bring the selections conversation forward. At close-out the same $21,000 would simply be a smaller number in the bank, with nothing left to decide.
09 / FAQ
Common questions.
Cost to complete is only the remaining piece, the forecast of what it will still cost to finish the job from today. Forecast final cost is the whole-of-job number, cost to date plus commitments not yet invoiced plus the cost to complete on uncommitted work. Cost to complete is one of the three inputs to forecast final cost, not another name for it. The clearest way to keep them straight is that cost to complete is forward-looking only, while forecast final cost is the whole build, the part already spent and the part still to come, in one figure.
Forecast final margin is forecast final revenue, which is contract value plus approved variations, minus forecast final cost. The level tells you whether the job is in front today. The movement between one review and the next tells you which way the job is heading, and that is the earlier signal. A margin that is still positive but has moved two points the wrong way in a month is a job developing a problem, and catching it there, while the causes are still visible and the decisions still open, is the whole point of forecasting rather than accounting after the fact.
Percentage complete on a cost basis is cost to date divided by forecast final cost, so the accuracy of the forecast final cost drives the accuracy of the WIP position directly. If the forecast final cost is understated because uncommitted lines were left at budget, the percentage complete is overstated, and the work-in-progress position reports more of the job done than has actually been done. How that percentage translates into recognised revenue is an accounting treatment to settle with the builder’s accountant. The builder’s job is keeping the denominator honest enough to be worth the accounting.
Common practice among builders who run this well is monthly at minimum, refreshed at every progress claim, and reworked on every major variation. The claim link is the non-negotiable one, because a claim asserts a percentage of the job is complete and that assertion rests on the forecast final cost underneath it. In a rising-cost market the forecast decays faster, so a cadence that was comfortable in a flat market is usually too slow. The refresh is cheap when the cost data is current, because cost to date and commitments are already recorded and the review only has to judge the uncommitted lines.
On both sides at once. An approved variation adds the cost of the changed work to the forecast final cost and the agreed price of it to the forecast final revenue, so the forecast final margin moves only by the real effect of the change. Recording one side and not the other is a common failure, usually the cost side lands in the numbers while the revenue side waits on paperwork. Work proceeding on an unpriced instruction is carried as visible forecast risk, cost exposure without matching revenue, until the variation is priced and signed.
It converges. Early on, most of the job is uncommitted and the cost to complete carries real uncertainty, so the forecast final cost is a wide estimate. As packages are ordered, lines migrate from judgement to commitment and the band of possible outcomes narrows. The forecast final margin should move for stated reasons and settle as the job closes out, so the final account confirms the forecast rather than surprising it. A forecast final cost glued to budget for eight months that then jumps at close-out was never a forecast, it was the budget wearing a different heading.
10 / Terms
Glossary for this topic
Forecast final cost (the whole-of-job estimate of what the job will have cost when finished, also called estimated final cost or cost at completion), cost to date (actual costs invoiced and coded to the job), committed cost (money promised by an order or subcontract but not yet invoiced), cost to complete (the forecast of remaining spend on uncommitted work), forecast final revenue (contract value plus approved variations), forecast final margin (forecast final revenue minus forecast final cost), forecast movement (the change in the margin between reviews, always with a reason). Definitions for the wider vocabulary live in the construction glossary.
Once the forecast final cost is honest, the question that follows is what it says about whether the builder is ahead of or behind the money already claimed, which is the subject of overbilling versus underbilling.
11 / Keep reading
Related knowledge, guides and features
12 / Further reading
Primary sources
- Australian Securities and Investments Commission , publisher of the insolvency statistics behind the external administration figures, the reference for current numbers.
- Australian Institute of Quantity Surveyors , professional guidance on cost management practice, including forecasting cost at completion against commitment.
- Your state or territory's building regulator and fair trading body, for the domestic building contract rules that govern how the variations feeding a forecast must be documented and approved.
- Your accountant, for how forecast final cost and WIP translate into recognised revenue for your business structure.
Know what the whole job will cost while you can still change it.
VIABUILD holds cost to date, committed and forecast against every cost code as the job runs, so forecast final cost and the margin on it are a live number the business can steer by, not a spreadsheet rebuilt at close-out.