Documentation 19.0

Sales & Quotations

Invoice a project progressively

2 min read Updated 2026-08-21 WindoorERP 19.0

What this does

Bills a project in stages against what has actually been completed, instead of invoicing the whole contract at the end — the way fabrication and installation contracts are normally paid.

Before you start

  • The order must be confirmed, with the lines that will be billed progressively already on it.
  • Agree with the customer what "progress" means for this contract: a percentage of each line, or a quantity delivered.

Steps

  1. 01
    Open the confirmed sales order.
  2. 02
    Open the progressive billing screen from the order.
  3. 03
    Enter this period's progress per line — as a percentage of the line, or as a quantity, whichever your contract uses.
  4. 04
    Check the calculated amount: it is this period's progress minus everything already certified on previous invoices.
  5. 05
    Submit the application for approval.
  6. 06
    Once approved, create the invoice from it.

How the cumulative model works

Each application states the cumulative position of the job, not the increment. The system deducts what was invoiced before and bills the difference. That is what keeps a long project's invoices adding up to the contract value, no matter how the percentages moved along the way.

Example

A curtain-wall package is 30% complete at the end of month one and invoiced accordingly. At the end of month two the site is 55% complete: the second application is entered as 55%, and the invoice is raised for the 25% difference — not for 55% again.

Advances and retention

  • An advance taken at the start is recovered against later applications rather than sitting as a credit nobody reconciles.
  • Retention is withheld per application and released later, so the amount held is always visible on the job.

Warning

Do not raise ordinary invoices on a job that is being billed progressively. The two methods keep separate ideas of what has been billed, and reconciling them afterwards is manual work.

Common mistakes

  • Entering the increment instead of the cumulative figure, and under-billing the job by everything already certified.
  • Invoicing progress that the site has not signed for.
  • Forgetting the retention release at the end of the defects period — it is money the company is owed.

Continue learning

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