Cart and checkout validation adds billing address and PO number error targets
Shopify developer change
MerchantDiff detected this entry in Shopify's official developer changelog on April 01, 2026.
This Shopify update is categorized as API, New, Functions, 2026-04.
What changed
Input graph fields: billingAddress and poNumber are available on all Shopify Function input graphs. They return null outside of Cart and Checkout Validation. Supported checkout field targets for error messages in Cart and Checkout Validation: $.cart.billingAddress.{field} (all standard address subfields) $.cart.poNumber Impact No breaking changes. Your existing functions continue to run. You can optionally add validations for these targets.
Who is affected
Developers building or maintaining Shopify checkout customizations should review this change.
What action may be needed
Review whether the new capability is relevant to your app. If you plan to use it, test the affected API or workflow before adopting it in production.
Use the official Shopify entry below as the source of truth for technical implementation details, affected APIs, migration instructions and deadlines.
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