System 01 leaves you with two numbers per job and a gap between them: the margin you signed up for, and the margin you ended up with. “We lost margin” is where most businesses stop, and it is the least useful thing you can know, because the four things that produce it have nothing in common and none of them respond to the same fix.
The idea in one line: the difference between intended and realized margin is made of exactly four gaps, they can be measured separately, and they have to add up — which is what stops a brief from counting the same dollar twice.
01
Four gaps, and only four
The quote gap
The job cost more than you said it would. Actual cost above the cost you estimated when you set the price. The money was never in the price to begin with.
The billing gap
You delivered work and never invoiced it. Extra hours, extra materials, the favour on site. Earned, never asked for.
The write-down gap
You invoiced deliberately below what you earned. A goodwill discount, a rounded-down total, a line quietly dropped because the customer would query it.
The collection gap
You invoiced and the money has not arrived. Late, short-paid, disputed, or written off. Asked for, never banked.
A business usually believes it has one of these and usually has three. They feel identical from the inside — each one arrives as a month that came in thinner than expected — and they are found in four different places in the records.
02
The arithmetic that proves you found all of it
This is the part that makes the audit hard to argue with, and it is the part most reviews skip.
The identity
Intended margin: quoted price − estimated cost.
Realized margin: collected − actual cost.
The four gaps: (actual cost − estimated cost) + (quoted − invoiced, split into never billed and written down) + (invoiced − collected).
The one rule that keeps it honest: work you agreed to do beyond the original scope belongs in the quoted price and in estimated cost, at what it should have been charged and what it took. In both, or in neither. A job where the extra went into neither reads as an overrun; a job where it went into only one is arithmetic that cannot be trusted.
Those two lines always come to the same number. Not approximately: exactly, by construction. If your four gaps do not sum to intended margin minus realized margin, something is either missing or being counted twice, and you know that before you show it to anyone.
It also settles the argument about the dollar that could go in two places. A discount given because the job ran late is a write-down, not an overrun, even though the overrun caused it. Every dollar lands in exactly one gap, and the cause gets written next to it rather than added to it.
03
Telling them apart
Each gap has a signature and a place it can be confirmed. If you cannot say which record a dollar came out of, it is not sized yet.
Where each one is found
Quote gap: compare the estimate as it stood at quote time against job costing. Watch for the estimate that was revised later, which makes the gap disappear on paper.
Billing gap: recorded hours and materials against the job, compared with what was invoiced. This one is invisible in the accounting system, because an invoice that was never raised leaves no record anywhere. It is found in the timesheet, the supplier invoice, the job notes, and the walkthrough.
Write-down gap: the invoice itself, against the priced work behind it. Usually visible as a discount line, a rounded total, or an invoice smaller than the quote with no change order to explain it.
Collection gap: the aged receivable at the date you pulled it, matched back to jobs. Separate genuinely late money from money nobody ever expects to see, and say which is which.
The billing gap is the one that hides best and is usually the most fixable. If the evidence for it is only the walkthrough, keep it and label it as the owner’s estimate rather than dropping it — but then say plainly what would have to be recorded for the next run to measure it.
04
Three sizing rules
1
One dollar, one gap. Nested causes get written as causes, never added as amounts. Otherwise the second trip shows up in the quote gap and again in the write-down that followed it, and the total stops being a total.
2
Report the four, never the one. A single “margin leakage” figure is the least actionable number in the brief and the easiest to attack. The four components with their jobs attached survive a hostile reading; the sum on its own does not.
3
Annualizing is a separate claim. A quarter’s gap multiplied by four assumes the mix repeats. Sometimes it does. Say so out loud and separately, so the reader can reject the annual number without rejecting the finding.
05
One bad job, or every job of a kind
The same gap of the same size means two completely different things depending on how it is distributed, and this is the question the brief exists to answer.
Sort every gap twice
By size: which jobs carry most of it. If three jobs out of forty hold eighty percent of a gap, you have three stories to go and check, and probably a customer or a crew in common.
By kind: group by type of work, customer, who priced it, and who delivered it. A gap that appears in nearly every job of one kind is a property of that work, which means it is a pricing or a process decision rather than a story about a bad week.
Compare a job only against the distribution of your own finished jobs. Published overrun ranges and realization-rate averages come from companies selling the software that fixes them, with no disclosed sample and no shared definition of what counts. Forty of your own jobs tell you what normal is here, which is the only comparison that supports a decision.
06
A worked example
The eleven-person electrical contractor from System 01. Forty-one finished jobs in one quarter, and an owner who was confident the quarter went wrong because of one commercial job.
The quarter, reconciled
Intended margin: quoted $612,400 − estimated cost $428,700 = $183,700, or 30.0% of quoted.
Realized margin: collected $539,800 − actual cost $461,900 = $77,900, or 12.7%.
Quote gap: $33,200. The commercial job accounts for $9,400 of it. $19,100 is second trips on residential service calls, across fourteen jobs. The rest is spread thin.
Billing gap: $27,600. Fourteen jobs where extra work was agreed on site and never added to an invoice. Largest $4,100, median $1,450.
Write-down gap: $10,700 across four invoices, three of them for the same customer, totalling $7,900.
Collection gap: $34,300. One tenant fit-out holds $28,400 of it, 74 days past its final invoice.
33,200 + 27,600 + 10,700 + 34,300 = $105,800, and 183,700 − 77,900 = $105,800. The four gaps close on the margin they explain, so nothing is missing and nothing is counted twice.
The job the owner blamed was the eighth largest line in the quarter. The largest single item is money already invoiced and sitting with one customer, and the most systemic one is the billing gap: fourteen separate occasions where somebody agreed to do more work while standing in a customer’s kitchen and no price followed. Those are three different problems with three different owners, and none of them is the one that was being discussed.
Do this step with an AI assistant
With the job ledger from System 01 already in the conversation, send these three messages in order.
“Split the difference between intended and realized margin into four gaps: cost above estimate, delivered and never invoiced, invoiced below what was earned, and invoiced and not collected. Put every dollar in exactly one gap and cite the jobs behind each.”
“Now show me that the four gaps sum to intended margin minus realized margin. If they do not, tell me what is missing rather than adjusting a figure to make it close.”
“For each gap, tell me whether it is concentrated in a few jobs or runs through nearly every job of one kind, grouping by type of work, customer, who priced it, and who delivered it. Compare against the spread of my own jobs and no outside figure.”
Four gaps, each sized, each tied to named jobs, and an identity that proves the list is complete. That is a diagnosis, and it is still not a decision: a quote gap that runs through every job of a kind needs a different answer from one sitting in a single bad week, and the collection gap may not be about chasing at all. System 03 gives each gap the decision it actually needs.
