Numbering purchase orders

A good PO number does three jobs. It's unique. It's easy to say over the phone, even when the line is bad and the supplier is in a hurry. And it tells you something at a glance. Keep it short.

What you need first

• A decision on who issues numbers, so two people never use the same one.
• One place where numbers are kept, such as your PO software or one log sheet.
• A rule for what happens to a cancelled number.
• A rule for what you do when you restart the count, such as at the start of a financial year.

A simple pattern

Build the number from parts:

• A prefix. Letters that mark the document type, such as PO. It stops a PO number being mistaken for an invoice number or a job number.
• A year or period marker. Optional. It groups orders by year.
• A running counter. It goes up by one for each new order. Pad it with zeros so the numbers sort in order.

Put together, you get something like PO, then the year, then a counter. Pick your own order for the parts. Then stick with it, because a number format that changes every few months makes old records hard to search.

What the software does

Many products can manage the counter for you. ERPNext's manual is one example, and it says masters and transactions can be given prefixes in the form of naming series.¹

Some details from that manual:

• Each series needs its own unique prefix.¹
• A series can include the financial year, and it's common to have a separate series for each financial year.¹
• You can change the starting or current sequence number of an existing series.¹

Other products have their own settings and their own names for them. Check your maker's help pages for the exact steps.

Rules that save trouble

• Never reuse a number. If a PO is cancelled, keep the number and mark it cancelled. A gap in the list is easier to explain than two orders with one number.
• Don't put meaning in too many digits. Supplier codes, department codes and dates all in one number gets hard to read.
• Keep one series per document type. POs get one, invoices get another.
• Don't edit the counter by hand without a reason. Software lets you do it, but it's easy to cause a clash.
• Ask for the number back. Ask the supplier to quote your PO number on the packing slip and the invoice.

Why suppliers need your number on their bills

The PO number is how a bill finds its order. Wikipedia notes that some organizations return invoices that don't refer to a purchase order number to the supplier unpaid.² You may not go that far. But if a supplier leaves the number off, you have to match by hand.

Finding a PO later

Numbering helps when you search. Here's what to record next to each number:

• The supplier name.
• The date.
• The status: draft, sent, part received, complete, cancelled.
• Who approved it. Approval rules explains why.

Then, when a delivery turns up, you can look up the order in a few seconds. That's the whole point. What to do when the truck arrives is on the receiving page.

If you're starting from a mess

Don't renumber old orders. Start a new series on a clean date. Write down the old range and where those records live. From then on, use the new pattern for every order.