PO format rules

Requiring a PO number is not the same as checking format, prefix, regex, or length

Direct answer. Shopify B2B lets company buyers enter a purchase-order number and lets you set Net payment terms on a company location, but Shopify has no built-in no-code setting for PO format, prefix, regex, or length — a Cart and Checkout Validation function can read cart.poNumber (API 2026-04) and return field errors on $.cart.poNumber. B2B PO Guard — Require PO is that validation function: it checks format, prefix, regex, length, and uniqueness, and previews any PO rule live against a sample number before you publish.

B2B PO Guard — Require PO (Shopify App Store) validates PO numbers by format, prefix, regex, length, and uniqueness, sets deposit percentage guardrails, routes orders above a threshold for manual review, and previews any PO rule live against a sample number before you publish. This page is the format / prefix / regex / length slice — not uniqueness, deposit, threshold, or D2C no-op. Free includes one live PO rule with a monthly order cap. Deposit guardrails and review routing are paid features. This page is not legal advice.

Related: PO Box Blocker — AddressFence — Free blocks PO Boxes and parcel lockers on the shipping address at checkout, plus a small set of ZIP rules. Street-number checks and billing-address rules are on a paid plan.

Free check first: PO number format tester runs in your browser and sends nothing. Test prefix, length, characters, regex and duplicates on sample PO numbers.

Required is a boolean; format is a pattern

A require-PO rule only asks whether the field is empty. Format, prefix, regex, and length decide whether the string matches your company convention. Uniqueness is yet another rule against previously used numbers.

Install B2B PO Guard — Require PO → set PO format rules → preview a sample

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