A milestone is controllable only when the event, applicable lines, evidence package, reviewer, review period, exception route and payment consequence are written before the invoice arrives.
A schedule says '30% deposit, 40% after production, 30% before shipment'. It does not define production, identify the covered openings, require an inspection record, address approved changes or say what happens when three units are held while the rest are ready. The percentages look precise; the evidence is not. This guide shows how parties can structure objective milestone records for specialist window and door packages. It deliberately supplies no recommended percentages, legal wording or conclusion about when a particular payment is due.
1. Give every milestone an evidence anatomy
Define the milestone event in observable terms and tie it to contract line IDs and quantities. 'Materials ready' might otherwise mean ordered, delivered to the factory, visually checked, traceable to a lot, or approved for use. 'Production complete' might exclude glazing, hardware adjustment, inspection, packing or documentation. The contract team must choose and authorise the actual definition; the supplier should not infer it later.
For each event, specify the evidence package, issuer, reviewer/certifier, submission method, review period, discrepancy route and partial-achievement rule. Separate evidence creation from evidence approval. A dated factory record can show that an activity was recorded; it does not automatically establish conformity, contractual acceptance or payment entitlement.
UNCITRAL's CISG provides a legal framework for international sales where it applies, including buyer payment obligations and rules concerning time/place of payment and examination/non-conformity notices. It does not supply a custom milestone schedule for a window package. Parties need transaction-specific drafting and applicable-law advice rather than assuming a template overrides the Convention or domestic law.
| Field | Required decision | Unsafe substitute |
|---|---|---|
| Event | Objectively described state and exclusions | 'Ready' or 'substantially complete' without definition |
| Scope | Applicable line IDs, quantities and current revisions | A percentage of the undifferentiated project total |
| Evidence | Named records, format, issuer and applicability | Photos alone or an informal message |
| Review | Authorised reviewer, review window and status vocabulary | Silence treated as approval without an agreed basis |
| Exceptions | Partial, failed, disputed or changed-line procedure | Holding or paying the whole project by default |
| Payment consequence | Authorised calculation, invoice route and timing | Assuming evidence acceptance equals product acceptance |
2. Match evidence to the stage and the actual lines
An initial-payment stage may require the executed agreement, compliant invoice and any expressly agreed security or administrative records. It should not be described as evidence that goods exist. A design-release stage can point to approved submittals and a frozen line schedule, but approval of drawings is not proof of manufacture. A material or production stage needs traceability and inspection records matched to the affected lines, not generic factory photographs.
Shipment evidence should reconcile released quantities to package IDs, packing list, transport booking/document and the selected Incoterms reference. A transport document can evidence a carrier event within its terms; it is not universal proof of product conformity, destination receipt or acceptance. Delivery evidence should record the named receiving point, quantities and visible exceptions without forcing the receiver to certify concealed quality that could not reasonably be examined.
Handover or final-payment evidence may include an agreed document index, outstanding-item register and authorised completion/acceptance record. Keep warranty commencement, risk transfer, title, commissioning, practical completion and final acceptance separate unless the signed terms expressly connect them. Do not manufacture a single 'completion certificate' that collapses legally distinct events.
| Possible stage | Evidence candidates | What it does not prove by itself |
|---|---|---|
| Contract/start | Executed documents, controlled line baseline, compliant invoice, agreed security record if any | Materials purchased or production started |
| Technical release | Approved submittals and released line register | Manufacture, conformity or shipment |
| Materials/production | Line/lot traceability, dated process and agreed inspection records | Project acceptance or destination condition |
| Pre-shipment | Reconciled inspection disposition, packing list, package map and release | Carrier receipt or delivery |
| Shipment/delivery | Applicable transport document and receiving/exception record | Concealed conformity or final acceptance |
| Handover/close-out | Agreed document index, open-item status and authorised certificate where required | Legal finality beyond the signed terms |
3. Use the project quality plan to generate evidence, not payment conclusions
ISO 10005:2018 offers guidance on quality plans: establishing the plan, its inputs, content, operation, review and revision. A contract-specific plan can identify responsibilities, resources, processes, monitoring, inspection and documented information. This makes it a strong source for the evidence pipeline, but the quality plan should not create payment entitlement unless the signed commercial documents expressly assign that function.
Build a milestone evidence index from the approved quality plan and inspection/test plan. For each record, capture its identifier, revision, applicable line/lot, creator, date, required witness/review, disposition and superseded status. Protect original records and keep corrections traceable. A folder containing many PDFs is not an evidence package if the reviewer cannot map them to the claimed units and milestone.
If sampling inspection is contractually adopted, define the approved plan and lot formation. ISO 2859-1 provides an acceptance-sampling system indexed by AQL, but AQL is not a promise that a certain percentage of defects is acceptable in every delivered unit, nor should this article select a plan. Record failed or inconclusive outcomes and the authorised reinspection/concession/rework route before claiming the affected milestone.
| Field | Purpose | Audit question |
|---|---|---|
| Record ID/revision | Controls document identity | Is this the current authorised record? |
| Line/lot applicability | Maps evidence to claimed scope | Which exact units does it cover? |
| Method/criteria reference | Connects the check to the approved basis | Was an unagreed criterion introduced? |
| Creator/witness/reviewer | Separates evidence generation and decision roles | Did the authorised party perform the required review? |
| Result/disposition | Preserves pass, fail, hold, concession or superseded state | Is an unresolved exception hidden? |
| Milestone link | Supports calculation without redefining entitlement | Does the commercial document actually require this record? |
4. Design for partial completion, changes and evidence disagreement
Window packages rarely move as one indivisible block. Define whether a milestone can be claimed by line, lot, shipment or another authorised unit. The calculation must be reproducible from the contract schedule and must prevent duplicate claims. Show prior certified/paid amounts, current eligible scope, held scope, approved changes and cumulative balance without implying that arithmetic itself establishes entitlement.
Changes can invalidate milestone evidence. When glass, hardware, finish, dimensions, quantity, delivery point or evidence requirements change, identify affected lines and decide whether previous approval remains applicable. Link the authorised change and revised value/basis before the next claim. Never relabel the old evidence to fit the new configuration.
Create a neutral discrepancy path: submitter's claim; reviewer response by line and evidence item; status such as accepted for stated milestone, clarification required, rejected with reason, or outside reviewer authority; correction/resubmission; escalation under the signed contract. Preserve both versions and timestamps. This record supports resolution but does not decide legal breach, interest, suspension, termination or other remedies.
| Control | Record | Check |
|---|---|---|
| Eligible scope | Line/lot IDs, quantity, authorised value basis | No unreleased or superseded line included |
| Evidence state | Required evidence and reviewer disposition | No submitted-only record counted as accepted |
| Prior claims | Prior claimed/certified/paid amounts kept distinct | No duplicate quantity or value |
| Exceptions | Held, failed, disputed or changed items | Excluded or handled by agreed rule |
| Current calculation | Reproducible line-level arithmetic | Matches authorised currency/rounding/tax basis |
| Residual | Remaining scope/value without promise of entitlement | Reconciles to controlled baseline and changes |
5. Run a pre-invoice evidence check without self-certifying payment
Before issuing or reviewing a milestone invoice, reconcile the current signed commercial baseline, authorised changes, line states, required evidence index, reviewer dispositions, prior claims and open exceptions. The check should identify missing or mismatched records early. Its output is a submission-readiness or review record, not a legal determination that payment is due.
Keep banking instruments and documentary conditions on their own specialist route. A letter of credit or demand guarantee can depend on exact document wording and bank examination rules; operational evidence that satisfies a project reviewer may still be discrepant for a bank, and vice versa. Obtain authorised banking/legal review rather than copying milestone language into an instrument.
A good schedule can say: evidence received for lines A–D; line E held after configuration change; reviewer decision pending; invoice calculation excludes E. That is precise without claiming acceptance, waiving rights or inventing a remedy.
FAQ
What payment percentages should an overseas window order use?
There is no universal safe percentage. Structure and percentages depend on transaction risk, bargaining, law, credit, security, programme and financing; use authorised commercial/legal advice.
Are factory photos enough to prove production completion?
Usually not as a standalone control. They need identity, date, line/lot applicability and the contractually required review context.
Does approving milestone evidence accept the products?
Not automatically. Evidence review, payment entitlement, conformity, delivery and final acceptance are separate unless the signed terms expressly connect them.
Can part of a milestone be claimed?
Only under an agreed unit and calculation rule tied to eligible lines/lots and evidence, with duplicate-claim and exception controls.
Does the CISG define a deposit schedule?
No. The CISG contains rules for international sales where applicable, but it does not provide a project-specific percentage milestone schedule.
Can a failed inspection be omitted until the next invoice?
No. Preserve the result and route rework, reinspection, concession or dispute through the authorised process before claiming the affected scope.
Continue the project review
Connect this guide with the proposed window and door systems, then review how Cavorlen approaches manufacturing and quality control. When your schedule is ready, send it through the project review form.
Official sources used
UNCITRAL — CISG official text and explanatory material ↗UNCITRAL — Digest of Case Law on the CISG ↗ISO 10005:2018 — Quality management: guidelines for quality plans ↗ISO 2859-1:1999 — Sampling procedures for inspection by attributes ↗Related buyer guides
This article is not legal, banking, credit, accounting, tax, sanctions, insurance or contract advice. It does not recommend milestone percentages, deposits, retentions, securities, letters of credit, remedies, deemed approvals or title/risk arrangements; determine payment entitlement or acceptance; or state any Cavorlen payment term, financial position, capacity or service. Authorised commercial/legal advisers, banks where involved, the signed contract and applicable law control the transaction.