(Use Case) One Per Customer (Limit to 1 per person)

Use case

Use this for limited-quantity commemorative items, first-come-first-served special products, and similar situations where you want to prevent customers from making repeat purchases.

Important notes

This setup uses Shopify Flow. If you have not installed it yet, please do so in advance.
Because this setup relies on Shopify Flow's tagging process, there is a brief time lag between order completion and tag application. If a new order is placed during this window, it may bypass the restriction.

Result

Customer status	Result	Reason
Logged in + not yet purchased (no tag)	Allowed (max 1 item)	Does not have the restriction tag
Logged in + already purchased (has tag)	Not allowed	Purchase completion tag has been applied
Not logged in (guest)	Not allowed	Account required — not authenticated

Setup flow

Step 1: Create a customer rule

Create a customer rule that blocks purchases from customers with the "purchased" tag.

Field	Value
① Title	Enter any title
② Limit details > Customer accounts	Require account
② Limit details > Customer tags	Customers with the tags below are not allowed to make purchases: `purchased`
③ Eligible items	Set the products or collections you want to restrict
④ Product message	Enter any message
⑤ Alert message > Display timing	Cart updated and checkout
⑤ Alert message > Message	Enter any message

If you want to allow guest purchases, uncheck Require account. However, changing this setting means the restriction check will only run on the checkout page. Please note that restriction checks will not be performed on product pages or the cart page.

Step 2: Create a product quantity rule

Create a product quantity rule that limits purchases to a maximum of 1 item per order.

Field	Value
① Title	Enter any title
② Limit details > Maximum quantity	1
② Limit details > Applicability	Variant
③ Eligible items	Set the products or collections you want to restrict
④ Product message	Enter any message
⑤ Alert message > Maximum quantity message	Enter any message

Step 3: Create a Shopify Flow workflow

Create a Shopify Flow workflow that automatically adds the "purchased" tag to customers when an order is completed.

Trigger: Order created
Condition: Orders containing the target product
Action: Add the purchased tag to the customer