Use this when a client gives you a purchase order number and you want it on the invoice header (Reference), or when several deliverables on one project each have their own PO.
Where the client PO lives
Drum stores the client purchase order number on the project, not on each deliverable. Most accounts use a project custom field whose label includes “order number” (for example Purchase Order Number). Set that value on the project before you raise the invoice. See Add custom fields to projects for filtering and reporting.
This is separate from Drum’s supplier Purchase Orders (costs and commitments). Client PO is a billing reference for the invoice.
How it reaches the invoice
When you create a new project invoice, Drum prefills the invoice Reference field from the project by default, but only if Reference is still blank. Changing the project PO later does not rewrite existing invoices.
Default: the project’s purchase order number (from that order-number custom field).
Or the project number, if you change the default.
Change the source in Settings → Account Defaults → Default invoice reference field (Purchase order number or Project number).
If the project has a purchase order number, Drum can also include it on the optional project summary line on the invoice (labelled PO/Reference Number). You can still edit Reference on the draft invoice before you approve it.
When the invoice syncs to finance, Reference is sent as the Xero invoice Reference, or as MYOB CustomerPurchaseOrderNumber.
Different POs per deliverable
Drum does not store a client PO per deliverable. If one project has several client POs (one per deliverable or phase):
Put the PO in the deliverable description so the team can see it while claiming.
When you raise the invoice or claim for that work, copy the right PO into the invoice Reference field (or leave the project-level default if it already matches).
When you convert a progress claim
Converting a claim still fills the invoice Reference from Settings → Account Defaults → Default invoice reference field. The invoice structure you pick does not change that.
The top description on Approve & Convert is separate from Reference.
A single invoice line, one line per claim item, and one line per claim item with costs on their own lines all use the project summary. If the project has a purchase order number, that summary includes a line labelled PO/Reference Number. The version with costs on their own lines is shorter (no contact email).
If your account offers the structure that consolidates time and costs into single lines, that description is the project number, the project name, and the claim name. It does not include PO/Reference Number. The menu uses your account’s names for time and costs. That is how the structure is built, not a setting you can turn on.
Need the purchase order in that top description? Edit it on Approve & Convert before you confirm.