Cost Loading and Cash Flow
Last reviewed 9 September 20263,139 words14 min read
Putting money on the bars — and what the early/late envelope actually tells the client
🟩 In one line: Load cost to match the payment breakdown (not the estimate), let P6 spread it by the resource or expense curve, and read the early and late cost curves as the envelope within which the real cash flow must fall — then apply payment terms, retention and advance payment in the spreadsheet, not in P6.
👤 Who this is for: Mid-level planners asked for a cost-loaded programme or a cash-flow forecast; senior planners agreeing the method with the QS. Prerequisites: Resource-loading-and-histograms, Wbs-structure-design, S-curves-early-late-actual.
First, let's be honest about why this page exists
Most cost-loaded programmes are built the night before the tender close by dividing the contract sum across activities in proportion to duration. They satisfy a specification clause and nothing else: the cash flow they produce is a straight line, the QS ignores it, and when the Employer's finance team compares it to the first three valuations it is 40 % out.
A useful cost load has one property — an activity's cost is what the payment application will claim when that activity is done. That means the schedule's WBS and the BOQ or payment breakdown have to agree, which is a decision made at set-up, not at loading.
🟨 The standard — what "good" looks like
| Source | What it says (paraphrased) | Use it for |
|---|---|---|
| FIDIC 1999 Cl 14.4 / 2017 Cl 14.4 (Schedule of Payments) | Where a schedule of payments is used, it may be tied to programme progress; revised estimates of payments submitted (check against your copy) | Contractual link between programme and cash flow |
| FIDIC 1999 Cl 14.4 (cash-flow estimate) / 2017 Cl 14.4 | Contractor submits a non-binding estimate of payments in quarterly periods, revised (check against your copy) | The cash-flow deliverable |
| FIDIC 1999 Cl 14.2, 14.3, 14.9 / 2017 Cl 14.2, 14.3, 14.9 | Advance payment and repayment; retention percentage and limit; release of retention at taking over and DNP end (check against your copy) | The three adjustments applied after P6 |
| FIDIC 1999 Cl 14.7 / 2017 Cl 14.7 | Payment timing after the statement / IPC (check against your copy) | The payment lag |
| NEC3 / NEC4 Cl 50, 51, Option X14 (advanced payment), X16 (retention) | Assessment dates and payment; advanced payment; retention as secondary option (check the clause numbers in your contract) | NEC equivalents |
| NEC3 / NEC4 Cl 31.2; Option A/C activity schedule | Programme content; Option A payment by completed activities on the Activity Schedule | Under Option A the activity schedule is the cost load |
| AACE RP 34R-05 Basis of Estimate; RP 38R-06 | Estimate basis and schedule basis reconciled; cost loading documented | SBM section on cost basis |
| DCMA 14-Point, item 10 | Cost or resource on every activity | Coverage |
| GAO Best Practice 5 and 9 (integrating cost and schedule) | Costs assigned to schedule activities; schedule and estimate consistent | Integration test |
| Hub convention | WBS L1–3 match the payment breakdown; cost in P6 as budget; payment mechanics outside P6; early/late curves from Project Baseline | Your defaults |
🟢 Rule: cost per activity = what gets certified when it is done; P6 produces the earned-value curve; the spreadsheet turns it into cash.
How it actually works
1. Decide the method with the QS before loading.
| Contract type | Cost source | Load to |
|---|---|---|
| Re-measurable BOQ (FIDIC Red) | BOQ items mapped to activities via the quantity sheet | Quantity resources with Price/Unit = BOQ rate, or activity Expenses per BOQ item |
| Lump sum with payment breakdown (FIDIC Yellow / Silver, most Gulf D&B) | Payment breakdown line items — the schedule of values | Expenses on activities; WBS L1–3 = breakdown structure |
| NEC Option A | Activity Schedule | One-to-one: each Activity Schedule item is a P6 activity or WBS group; paid when complete |
| NEC Option C | Defined Cost forecast | Resource-based costing; the target sits as the baseline budget |
| Milestone payments | Payment milestones | Expense on the PAYMENT-coded milestone; zero elsewhere for that scope |
The test in every case: sum of activity costs per WBS L3 node = the payment breakdown line for that node, to the dirham. If it does not reconcile, loading has not finished.
2. Where the money goes in P6.
| Element | Path (check against your P6 version) | Use |
|---|---|---|
| Cost Accounts | Enterprise → Cost Accounts | Mirror the payment breakdown or BOQ sections; assigned to each resource assignment or expense |
| Resource cost | Resource assignment Price/Unit × Budgeted Units | Only when the payment is genuinely per unit measured (re-measurable) |
| Expenses | Activity Details → Expenses tab: category, cost account, Budgeted Cost, accrual type | Lump-sum breakdown, prelims, procurement payments, milestone sums |
| Accrual type | Start of activity / Uniform / End of activity | Uniform for production; End for approvals and delivery payments; Start rarely |
| Project Details → Calculations | Link Budget and At Completion (baseline draft only); subtract actual from At Completion | Keeps EAC honest after progress |
| Project Details → Settings | Baseline for earned value = Project baseline | BCWS from the accepted revision |
Prelims: time-related prelims as Uniform expenses on the Prelims LOE activities (which stretch and shrink with the programme — that is the point); fixed prelims as Start or End expenses on mobilisation/demobilisation activities. Procurement: deposit at PO (Start expense on the PO activity), balance at delivery (End expense on delivery) — matches FIDIC Cl 14.5 off-site payment discussions.
3. Produce the curves. Activity Usage Profile or Tracking → cost, cumulative, Budgeted Total Cost, early and late bars, monthly. P6 spreads each activity's cost across its early dates and separately across its late dates; the cumulative early curve is the fastest the Contractor could earn; the late curve is the slowest without becoming late. Export both to the workbook monthly.
4. From earned value to cash — in the spreadsheet.
| Step | Adjustment | Source |
|---|---|---|
| a | Planned value per month from P6 (early, late, and current forecast) | Activity Usage Spreadsheet export |
| b | Deduct retention (e.g. 10 % to a 5 % cap — contract figure) | FIDIC Cl 14.3 / NEC X16 |
| c | Deduct advance-payment repayment per the contract formula (e.g. 25 % of each IPC once 10 % of the sum is certified — contract figure) | FIDIC Cl 14.2 / NEC X14 |
| d | Add advance payment receipt at its date | Cl 14.2 |
| e | Shift by the certification and payment lag (e.g. statement + 28 days to certify + 56 to pay under 1999 Red — verify) | Cl 14.6 / 14.7 |
| f | Add retention releases at taking over and end of DNP | Cl 14.9 |
| g | Result: Contractor cash-in curve. Cost-out curve (from the estimate phasing) is the commercial team's; the gap is the funding need | Commercial |
None of this goes into P6. P6 does not model payment terms, and trying to fake them with lags or expenses destroys the earned-value data.
5. Maintain it. At each update the forecast curve moves with the schedule automatically because expenses follow the activities. Actual cost is not the certified amount — certified is behind by the lag and net of retention. If the contract requires actuals in P6, enter certified gross value per activity from the IPA breakdown as Actual Cost, monthly, from the QS's sheet; otherwise leave Actual Cost blank and report earned value from physical % (which is what the QS's application should equal). Reconcile earned value in P6 to the gross application every month; a difference > 3 % is either a rules-of-credit problem or a front-loading problem, and it gets found.
📜 Front-loading, the envelope, and what you sign
- Front-loading — pricing early activities above their true cost so the early curve accelerates cash. The cost load must reconcile to the accepted payment breakdown; if that breakdown was front-loaded at tender the schedule inherits it honestly and the QS defends it. The planner does not re-weight it in P6 to make the curve look better; that is a document that will be compared to the breakdown.
- The envelope — an actual cumulative-value curve that sits between early and late is on programme; below late is behind, and the vertical gap in value, converted to months on the late curve, is a first estimate of the delay. Above early is either front-loading or a rules-of-credit problem; find out which.
- Non-binding — the FIDIC Cl 14.4 cash-flow estimate is expressly a non-binding estimate. Say so on the sheet. NEC Option A is different: the Activity Schedule defines payment, so changing an activity's price is a commercial act, not a planner's.
- Milestone payments — a PAYMENT-coded milestone paid on achievement puts the whole sum at one date. Under-progressing that milestone's predecessors shows a cash cliff in the forecast; that is a correct warning, not an error.
🟥 Where people go wrong
- Cost spread by duration. Contract sum ÷ total activity-days × each activity's days. The result is a straight line that matches nothing; the first valuation shows structure at 22 % of value versus 9 % in the programme. Load from the payment breakdown.
- WBS built before the payment breakdown was read. Level 3 nodes cut across breakdown lines and no node reconciles. The WBS decision on Wbs-structure-design — L1–3 match the payment breakdown — exists for this page.
- Payment terms modelled in P6. Lags for payment periods, expenses for retention. The earned-value baseline becomes unusable and the cash flow is still wrong. Payment mechanics belong in the workbook.
- Certified amount entered as earned value. Certified is net of retention, lagged and disputed. Earned value is physical % × budget; the two are reconciled, not equated.
- Cost on LOE that does not stretch. Time-related prelims loaded as a fixed lump on a 400-day LOE that is never re-forecast. LOE with Fixed Duration & Units/Time carries the daily rate and grows with the programme — which is what the prolongation argument later needs (see Prolongation-costs-basics).
- Resource cost and expense on the same scope. Steel-fixer manhours priced and a rebar expense for the same activity double-count. One or the other per scope, stated in the SBM cost basis.
- Curves from the current schedule labelled as baseline. The early/late envelope must come from the Project Baseline (the accepted revision); the forecast curve comes from the current update. Three lines, three sources, all named.
⚖️ When you're challenged
"Why does your cash flow show only 8 % earned by month six? The estimate says 15 %." The estimate phases cost, including mobilisation and procurement deposits; the programme phases the payment breakdown, which pays for installed work. Both are right for their purpose. The funding gap between them is the number the commercial team needs, and it's on sheet 3.
"The Employer says we've front-loaded the programme." The cost per WBS node reconciles to the accepted payment breakdown to the dirham — the reconciliation is in SBM §8. If the breakdown is weighted early, that was agreed at contract; the programme doesn't add to it.
"Just put the retention and payment terms into P6 so the curve is right." P6 spreads value by activity; it doesn't model contract payment terms, and if I fake them the earned-value baseline is destroyed. The value curve comes out of P6, the cash curve is built from it in the workbook with the contract's own percentages, and both are submitted.
"Actual value is below the late curve — how late are we?" Reading horizontally from the actual to the late curve gives about six weeks at today's earning rate. That's an indication, not a measurement — the measurement is the longest-path variance in the narrative, which says 31 working days. They agree closely enough to trust.
📄 Related pages
- WBS Structure Design — L1–3 must match the payment breakdown for any of this to work
- Resource Loading and Histograms — the manhours the cost sits on
- Earned Value Basics: SPI and CPI — BCWS, BCWP, ACWP from the curves built here
- S-Curves: Early, Late and Actual — presenting the envelope
- Prolongation costs basics — why prelims sit on stretching LOE
- Progress measurement and rules of credit — why earned value and the application should agree
- Monthly Progress Report — where the cash-flow sheet goes
- Redirect: cost-loading-a-schedule and cash-flow-forecasting are merged into this page
✏️ Worked example — Doha office tower, cost load and cash flow at baseline
Lump sum QAR 480 M; payment breakdown 62 lines; retention 10 % to 5 % cap; advance 15 % repaid at 20 % of each IPC from IPC 3; certify 28 days, pay 56 days (assumed — verify against the contract); 26-month programme.
Reconciliation extract (WBS L3 ↔ payment breakdown):
| WBS L3 node | Breakdown line(s) | Breakdown QAR M | Loaded QAR M | Diff |
|---|---|---|---|---|
| Substructure — raft & basements | 2.1, 2.2 | 38.4 | 38.4 | 0 |
| Superstructure — L1–L32 | 3.1–3.4 | 92.0 | 92.0 | 0 |
| Façade — unitised | 5.1, 5.2 | 71.5 | 71.5 | 0 |
| MEP — L1–L32 | 7.1–7.9 | 118.0 | 118.0 | 0 |
| Prelims (time-related) | 1.2 | 41.6 | 41.6 (Uniform on Prelims LOE, 26 mo) | 0 |
| Procurement — deposits | 8.1 | 14.2 | 14.2 (Start expense on PO activities) | 0 |
| … (56 further lines) | 0 | |||
| Total | 480.0 | 480.0 | 0 |
Curve extract (cumulative QAR M, from Project Baseline BL0):
| Month | Early value | Late value | Cash-in (early, after retention, advance, lag) |
|---|---|---|---|
| 0 | 0 | 0 | 72.0 (advance) |
| 3 | 28 | 19 | 72.0 |
| 6 | 68 | 46 | 92.6 |
| 9 | 121 | 88 | 131.1 |
| 12 | 189 | 148 | 181.5 |
| 15 | 264 | 218 | 240.2 |
| 18 | 336 | 291 | 302.9 |
| 21 | 402 | 366 | 364.4 |
| 24 | 458 | 432 | 416.1 |
| 26 | 480 | 480 | 439.7 + 12.0 retention release at TOC |
| DNP + 12 | — | — | +12.0 retention balance |
Read at DD month 12 (first use): Actual gross application cumulative QAR 156 M; earned value from P6 physical % QAR 158.4 M (1.5 % difference, within tolerance). 156 sits between late (148) and early (189): on programme but tracking the late curve — consistent with the narrative's 9 days of float remaining on Section 1. Cash-in received to date QAR 168 M against the early-case 181.5 M; the difference is payment-lag and one disputed IPC, not schedule — noted for the commercial team, not for the narrative.
📖 References
- FIDIC Conditions of Contract for Construction 1999, Cl 14.2, 14.3, 14.4, 14.5, 14.6, 14.7, 14.9 (check the edition in your contract)
- FIDIC Conditions of Contract 2017 editions, Cl 14.2, 14.3, 14.4, 14.5, 14.6, 14.7, 14.9 (check the edition in your contract)
- NEC3 / NEC4 ECC, Cl 31.2, 50, 51; Options A, C; Secondary Options X14, X16 (check the clause numbers in your contract)
- AACE International RP 34R-05, Basis of Estimate; RP 38R-06, Documenting the Schedule Basis
- DCMA 14-Point Schedule Assessment, item 10; GAO Schedule Assessment Guide GAO-16-89G, Best Practices 5 and 9
- Oracle Primavera P6 Professional User Guide — Cost Accounts; Expenses; Activity Usage Profile; Project Details Calculations (check against your P6 version)
From the field
Experience from working planners. Unreviewed — read it as experience, not guidance.
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