Purchase order

A purchase order (PO) is a buyer's written order to a supplier, listing what it wants, how many, at what price and by when, and once the supplier accepts it, it usually forms the contract for that order.

What it is

A PO starts inside the buying company. Someone requests the goods, a manager approves the spend, and the PO goes to the supplier. When the supplier accepts, by signing or by shipping, the PO and any terms it points to become the deal.

So there are two kinds of signature around a PO:

Internal sign-off. A budget holder approves the PO before it leaves the company.
Supplier acceptance. The supplier signs to confirm it will fill the order on these terms.

docuinked can collect both. It records who signed, when, and the exact file they saw. It does not move money, pay suppliers, or connect to accounting or ERP tools. Those stay in your own systems.

When it is used

Buying stock, parts or equipment from a supplier.
Any spend above a limit that needs a manager's approval.
Construction firms ordering materials for a job.
Freight and logistics teams buying fuel, parts or services.

What it usually contains

Section	What it covers
PO number and date	A unique number that the invoice will quote back
Buyer and supplier details	Names, addresses and contacts
Line items	Description, quantity, unit price and total for each item
Taxes and shipping	Added costs, and who pays them
Delivery details	Address, required date and delivery method
Payment terms	When the invoice will be paid after delivery
Terms and conditions	A link to or copy of the buyer's standard terms
Approval block	The internal approver's signature and date
Supplier acceptance	The supplier's signature, if the buyer asks for one

Things to get right

One PO number, everywhere. Put it in the document title and metadata, so the signed PDF, the invoice and your books all match.
Approve before it leaves. The internal sign-off should come first. Use signing order so the supplier never sees an unapproved PO.
Mind whose terms win. When a supplier replies with its own terms, the result can be unclear. Your lawyer can advise on wording.

General information only, not legal or accounting advice. Your finance lead and a lawyer should agree your PO terms.

How to send it for signature with docuinked

In the app

Upload the PO, add your approver as signer 1 and the supplier as signer 2, and turn on signing order. The supplier gets the link only after your approver signs.

By API

Your purchasing tool generates the PO as a PDF and sends it. The approver signs first, then the supplier. The PO number is the Idempotency-Key, so a retry never creates a second PO.

curl https://docuinked.com/v1/documents \
  -H "Authorization: Bearer $DOCUINKED_API_KEY" \
  -H "Idempotency-Key: po-2026-0931" \
  -H "Content-Type: application/json" \
  -d '{"title": "PO 2026-0931, steel brackets",
       "pdf_url": "https://example.com/po-2026-0931.pdf",
       "ordered": true,
       "metadata": {"po": "2026-0931"},
       "signers": [{"name": "Robin Hale", "email": "robin@example.com"},
                   {"name": "Supplier Orders", "email": "orders@example.net"}],
       "fields": [{"signer": 1, "kind": "signature", "anchor": "Approved by:"},
                  {"signer": 2, "kind": "signature", "anchor": "Accepted by supplier:"},
                  {"signer": 2, "kind": "date", "anchor": "Acceptance date:"}],
       "send": true}'

When document.completed arrives on your webhook, your own system marks the PO as accepted. That last step is yours to build. See n8n or Make for doing it without code.

From an agent

An agent can assemble a PO from a request and prepare it over MCP. A live send stops at an approval_url. That approval is a person releasing the draft to be sent. The approver's signature on the PO is a separate step, which only that person can do on the signing page. The agent can do neither. See approvals.

Sources

Checked 2026-11-07.

ESIGN Act, 15 USC 7001: electronic records and signatures may not be denied effect solely for being electronic.
ESIGN Act, 15 USC 7003: UCC Article 2, which covers sales of goods, stays within ESIGN's scope.

Common questions

Does a supplier have to sign a purchase order?

Not always. Many suppliers accept by shipping or by sending a confirmation. A signature gives you a clear record of acceptance, which helps on large or custom orders.

Can docuinked pay the supplier when the PO is signed?

No. docuinked records signatures and sends a webhook. Payment stays in your bank, accounting or ERP tools, which your own workflow can trigger from that webhook.

Who should approve a purchase order internally?

Whoever your spending policy names for that amount. Use their real email, because the evidence log records that exact person as the signer.

Try it in test mode

Free during the beta. Test keys send no email, so you can build the whole flow first.

Get an API key Read the quickstart