> For the complete documentation index, see [llms.txt](https://supercartapp.gitbook.io/supercart-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://supercartapp.gitbook.io/supercart-docs/other-features/checkout-validations.md).
# Checkout Validations
Prevent customers to purchase Extra Services add-ons alone
### How to enable?
Visit your Shopify Admin Section and click on the Checkout tab.
Scroll down to Checkout rules. Click on Add rule and select the Supercart validation.
Now you can turn on the validation.
### Result
The customers are not allowed to purchase Extra Services as single products.
