Billing match is not a PO Box block

Requiring shipping and billing to match does not detect PO Boxes — it only forces the two addresses to be identical

Direct answer. To require a street number (house number) or block a PO Box in the billing address on Shopify, use a checkout-validation app: Free on PO Box Blocker — AddressFence blocks PO Boxes and parcel lockers on the shipping address at checkout, plus a small set of ZIP rules. Requiring a street number and billing-address rules are on a paid plan. Built-in checkout rules cannot target billing at all.

PO Box Blocker — AddressFence (Shopify App Store). 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. Built-in checkout rules cannot target billing at all. Test any address in the simulator before publishing, with one-click rollback.

Related: B2B PO Guard — Require PO — B2B purchase order number required at company checkout.

Free check first: PO box and street number address checker runs in your browser and sends nothing. Paste addresses and see which look like a PO box or lack a street number.

Shopify’s “require shipping and billing address to match” preference is a fraud-control option. It makes the two addresses the same. It does not inspect either address for a PO Box. If the matched address is a PO Box, both sides remain a PO Box.

Install PO Box Blocker — AddressFence

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Native match preference: identical addresses, not a PO Box detector

Shopify Help: address collection preferences documents the control at Settings → Checkout → Address collection: Require shipping and billing address to match. The job is identical addresses. Help recommends it for stores with a high amount of fraudulent orders, paired with an Address Verification System. A side effect is that customers cannot send gifts to a different shipping address.

That preference does not read address lines for “PO Box”. Copying shipping into billing, or forcing the two fields to be the same, still leaves a PO Box on both sides when the shared address is a PO Box.

Native shipping format rules do not become a billing PO Box check

Shopify Help: address format validation in Checkout Blocks can block PO Box addresses on the shipping address. That rule has been available to all merchants since the 17 June 2026 changelog. Help states that only shipping addresses are validated, and that billing address fields are not supported and cannot be targeted by those rules.

Requiring billing to match shipping does not add a billing PO Box detector. The format rule still watches shipping. The match preference still only asks whether the two addresses are identical. A buyer who bills and ships the same PO Box still checks out with a PO Box on the card billing address.

Billing-targeted validation for a PO Box or missing street number

To reject a PO Box — or a missing street number — on the card billing address, publish checkout validation that reads billing. On AddressFence that job is a billing-address rule on a paid plan: built-in checkout rules cannot target billing at all. Free blocks shipping PO Boxes and parcel lockers, plus a small set of ZIP rules. The same listing covers “Require a street number so incomplete addresses are caught at checkout.” Test any address in the simulator before publishing, with one-click rollback.

Match preference vs billing-targeted checkout validation
Control	What it does	PO Box on billing?
Require shipping and billing to match	Forces the two addresses to be identical	No detector — a matched PO Box stays a PO Box on both sides
Checkout Blocks address format validation	Blocks non-compliant shipping formats, including PO Box	Billing fields are not validated by that rule
AddressFence billing-address rules	Checkout validation that can read the billing address	Rejects a PO Box on the card billing address when that rule is published

Install PO box blocker

Not the same as AVS, risk scores, carriers, or a purchase-order number

Not AVS or card-issuer address checks. Help pairs the match preference with an Address Verification System; matching shipping to billing is not that issuer check.
Not a change to Shopify’s order-risk score. Identical addresses are a checkout collection preference, not a risk-score rule.
Not carrier delivery restrictions. Hiding rates for a ship-to does not inspect the card billing address.
Not B2B purchase-order number rules. A PO number on an invoice is a different job: require a PO number at B2B checkout.
Not postal vs purchase-order confusion. Blocking a postal PO Box on billing is not the same as requiring a buyer’s PO number.

App path: billing-address rules and require a street number

Open the AddressFence listing (apps.shopify.com/address-guard) and install it.
Enable billing-address rules and require a street number as the listing describes: built-in checkout rules cannot target billing at all, and require a street number so incomplete addresses are caught at checkout. Test any address in the simulator before publishing, with one-click rollback.
Publish to checkout validation.

How-to for the broader billing job: PO box blocker for the billing address, not just shipping. Street number after Address Blocker sunset: require a street number at checkout.