One per customer, enforced

Subscribe & Save, Build-a-Box, Fixed Bundle and Mystery Box plans now have a One per customer card. Turning it on stops a logged-in customer from checking out with more than one subscription to that plan, active or paused, or adding more than one of it to the same cart.

The card opens a modal where the merchant sets the limit and writes the two messages shoppers see: one when a cart already holds more of the plan than it allows, and one when a returning customer who already holds the plan tries to add it again. Both messages fall back to a default if left blank.

Enforcement runs as a Shopify checkout validation, so the block happens at checkout itself rather than relying on the storefront to catch it first. The validation only applies to plans the merchant has turned the limit on for; every other plan, and every shop that leaves the setting off, checks out exactly as before.

The limit is off on every plan by default; a merchant turns it on per plan from that plan's page.