How to build a procure-to-pay integration

What matters here

• Check the budget before the approval, not after the invoice. A commitment made against an exhausted cost centre is already a problem.
• Hold the approval matrix as data. Thresholds and delegations change with every reorganisation and should not be a deployment.
• Match on three documents, not two. Order against invoice misses the goods that never arrived.
• Route exceptions to a named person with the discrepancy attached. A queue of unmatched invoices is where early payment discounts die.
• Record the commitment at PO, not at invoice. Committed spend is the number that makes a budget report honest.

Who this is for

You run finance systems or procurement operations. Purchase requests arrive by email, approvals happen in threads, and the first time finance sees a commitment is when the invoice lands.

How it works in practice

What has to happen between somebody needing something and a supplier being paid.

1. 1

   A requisition is raised with a cost centre and a category

   Not a free text description. Both drive the approval path and the budget check.

2. 2

   The budget is checked before anybody approves

   Committed plus actual against the line. An exhausted cost centre is a conversation now, not in six weeks.

3. 3

   The approval matrix routes on amount, category and cost centre

   Held as data, with delegation for anybody away, because a purchase waiting on somebody on leave is a stalled purchase.

4. 4

   An approved requisition becomes a purchase order

   And the commitment is recorded at that moment, not when the invoice arrives.

5. 5

   Receipt, order and invoice are matched three ways

   Within tolerance on price and quantity. Anything outside stops for a person.

6. 6

   Matched invoices clear for payment automatically

   The ones that did not match are the only ones anybody looks at, which is the point.

Paste these into Claude Code or Codex with the Tray Headless plugin installed. Each stage runs on its own. The systems named in them are the worked example rather than a requirement, and every prompt says so.

Once per project, run /tray-workflows:set-workspace to pick the workspace these build in. Point it at a sandbox first.

1. 1

   First, read the procurement and finance models

   Approval and budget both live in places the requester never sees.

   Headless skills build-workflow

   Copy

   Use build-workflow. The systems in play are Coupa and NetSuite, or
   whatever we run in those seats.
   
   I need the requisition, purchase order, receipt and invoice objects, plus
   the chart of accounts, cost centres and how budget is held per period.
   
   Specifically: where does committed spend live, and is it a real field or
   something everybody calculates in a spreadsheet. That answer decides most
   of this build.

2. 2

   Check the budget before anybody approves

   So the answer arrives while it can still change the decision.

   Headless skills build-workflow

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   Use build-workflow. On requisition submit, before routing for approval:
   
     Resolve the cost centre and the budget line from the category
     Sum posted actuals for the period
     Add open commitments from approved purchase orders not yet invoiced
     Compare against the budget for that line
   
   Show the requester the remaining budget before they submit, not after
   somebody approves. If the request would exceed the line, route it to the
   budget owner first regardless of amount.
   
   A commitment made against an exhausted cost centre is a problem that gets
   discovered in six weeks by somebody who cannot fix it.

3. 3

   Route on a matrix finance can edit

   Because thresholds change with every reorganisation.

   Copy

   Build the approval matrix as a table, not as logic:
   
     amount band, category, cost centre, approver role, and whether the
     approval is sequential or parallel
   
   Resolve approvers to real people through the directory at run time. Never
   hardcode a name, because the person who approved capital expenditure last
   year has changed role.
   
   Handle delegation: anybody marked away routes to their deputy
   automatically. A purchase request waiting five days on somebody on leave
   is a purchase that gets made on a personal card instead.
   
   Above a threshold I set, require two approvers and record both.

4. 4

   Match three ways, with tolerances

   Two-way matching pays for things that never arrived.

   Headless skills tray-gotchas

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   Use tray-gotchas, then build three-way matching between the purchase
   order, the goods receipt and the supplier invoice.
   
   Tolerances I can set: a small percentage or absolute on price, a
   percentage on quantity, and a window on date. Within tolerance clears
   automatically. Outside stops.
   
   Handle these explicitly:
   
     Partial delivery. Match what arrived, keep the remainder open, do not
     clear the whole invoice.
     Invoice before receipt. Hold rather than reject, because the goods are
     usually two days behind the paperwork.
     Price change between order and invoice. Always an exception, never a
     tolerance, because that is a supplier changing terms.
     Duplicate invoice number from the same supplier. Block it outright.

5. 5

   Route exceptions to a person, and report the commitment

   Because an unmatched queue nobody owns costs real money.

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   Every exception goes to a named person with the discrepancy shown side by
   side: what was ordered, what arrived, what was invoiced, and the
   difference highlighted.
   
   Do not build a queue that a team collectively owns. Assign each one.
   
   Then report: committed versus actual by cost centre, exceptions by reason
   and by age, early payment discounts available and how many were missed,
   and average days from requisition to purchase order.
   
   That last number is the one procurement is judged on and the one nobody
   measures.

6. 6

   Validate, then hand the matrix to finance

   Because approval thresholds are a finance policy.

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   Run the per-step schema checks and the whole-workflow audit before this
   touches production.
   
   Then open the same workflow in Tray Build so finance can maintain the
   approval matrix, the tolerances and the delegation rules in the visual
   canvas. Every reorganisation changes them.

What it connects to

Procurement holds the process, finance holds the money, and people need telling.

Named systems are the ones most teams run, not the only ones that work. Each is an authentication in your Tray workspace, referenced by name, so the workflow never holds a credential. Where we have a connector page, the name links to it.

Questions people ask

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