What certification requires depending on the contract's pricing system
In a lump sum contract, certification is based on progress of the agreed units or phases against the fixed total, and what must be demonstrated is percentage of actual execution, not cost incurred. In a unit price contract, each certified item needs contested or accepted measurement based on the measurement criterion set by the specifications, it is not enough to have executed the unit, you must be able to measure it by the same criterion it was budgeted. In a cost-plus contract, what is certified are actual costs justified with invoice, delivery note or timesheet, plus the percentage of overhead and profit margin agreed.
Confusing these criteria is the most expensive and most frequent error: applying lump sum logic (estimated physical progress) to a unit price contract, or accepting as certifiable an actual cost without supporting invoice in a cost-plus contract, generates certifications that do not hold up if the client or supervising architect questions them.
What documents each certification requires to not be challenged
A lump sum certification needs the progress report or statement that supports the claimed percentage, signed or at least reviewed by supervising architect. A unit price certification needs the measurement sheet with location, quantity and criterion applied, ideally verified on site before invoicing, a unilateral measurement without verification is the first to be questioned if there is discrepancy. A cost-plus certification needs the complete breakdown of invoices and delivery notes for the period, not an aggregated amount without documentary support behind it.
The time to gather this documentation is not when the client's review arrives, but at the moment of generating the certification. Reconstructing the support for a certification from three months ago, when items from different periods have already been mixed, is much slower and the result is weaker than if the support was already attached from the beginning.
Retentions, advances and price adjustment: what to check before signing
The guarantee retention (usually between 5% and 10% of each certificate, although the exact percentage depends on what was agreed in each contract) must be explicit in the contract with its return deadline tied to a verifiable milestone, provisional acceptance, final acceptance, end of guarantee period, and not to a generic date that no one controls. An advance, if it exists, needs its own agreed amortization mechanism: normally discounted proportionally from the first certificates, and that discount must appear explicit in each affected certificate so it is not confused with an unjustified reduction.
Price adjustment, when the contract contemplates it, requires an explicit formula or reference index and an application date, generic mention that 'prices will be adjusted based on cost variation' is not enough if the index and reference period are not set. Without that precision, adjustment ends up being negotiated case by case, which is exactly what a well-drafted contract should avoid.
Executed production vs. payment right: where the line is
Executing a work unit is a technical fact; whether that fact generates a payment right depends on whether it meets the contractual conditions for certification: accepted measurement, compliance with required quality, and in some contracts, prior approval if the unit involved a change from what was designed. An item executed with a material different from the specified, without prior approval of the change, may be physically executed and still not be certifiable under the agreed terms until that discrepancy is resolved.
This distinction is what generates the most friction between site and administration: whoever executes sees the work done and expects to bill it; whoever certifies needs complete contractual support before including it. Advancing the certification without that support, to not create tension with the subcontractor or client, transfers the risk to whoever signs the certification if it is later questioned.
How Bloqbase supports price, measurement and certification control
Bloqbase connects the Contract Analysis module with document management so the contract's pricing system identified, lump sum, unit price or cost-plus, remains linked to the associated measurements, invoices and certifications within the same work, instead of being managed in separate spreadsheets that have to be manually reconciled.
The tool does not decide whether a certification meets the contractual requirements to be issued: it orders the documentary support, measurements, invoices, approvals, so whoever certifies has that information gathered and can apply the correct contractual criterion on complete data.