Hello,
We have a Shopify store (not plus users) and are working toward a customized checkout without using the soon-to-be deprecated checkout page liquids. We are looking to add a custom note in our checkout that mentions if a product is Final Sale if it includes the tag “FINALSALE”.
I’ve found a thread with instructions for how to add a line-item level checkout note by using the buy-buttons.liquid file. Add Final Sale To Checkout - #5 by gr_trading
I want to know if the buy-buttons.liquid file will be deprecated, as it is adding a note that appears on the mini cart and cart pages. Shopify is recommending all updates be done by app, but I can’t find an existing app that is suitable for this customization. In the help documentation, I also cannot locate the exact list of liquid files that will be deprecated.
If anyone can help with this, I would appreciate it very much. Thank you!
line-item-properties, or cart-attributes are NOT going away just because the checkout is changing..
checkout.liquid and checkout-scripts deprecation are just that deprectations of those specific files.
Hi @tf-WLE-QCo 
cart and checkout are separate things.
buy-buttons.liquid is part of the frontend THEME system for the online store, not checkout.
checkoutliquid is used only for checkout; it’s confusing that is a part of a frontend theme but it would be even more confusing and harder to setup if it had to have it’s own admin/files area.
A line item property it’s important to use very specific terms , like not treating cart and checkout as the same word or system.
As a “note” is a cart-note, which is a cart-attribute.
Checkout modifications, for PLUS plans, are now being done using checkout-ui extensions which are less flexible than checkout.liquid
If you need deeper consulting to not be caught off guard with upcoming changes reach out to me.
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`buy-buttons.liquid` is part of your theme’s frontend, not checkout - it’s safe to customize and isn’t being deprecated. The only things going away are `checkout.liquid` and Additional Scripts, with the August 2026 deadline applying to Thank You / Order Status page customizations specifically. Your theme files, including `buy-buttons.liquid`, are completely unaffected.
For the “Final Sale” tag display, you’re on the right track - you can render a conditional in `buy-buttons.liquid` (or wherever your Add to Cart area lives) using `{% if product.tags contains ‘FINALSALE’ %}` and outputting whatever note or badge you want. That’s straightforward Liquid and won’t need to change. The checkout extensibility changes only come into play if you want that messaging to appear inside the checkout flow itself, which is a separate problem requiring a UI extension.
And you’re positive you want this FINAL SALE text to be an item property (displays under every item) and not a cart attribute (cart note)? 
Hi Paul,
Thank you for the detailed explanation. I apologize for not using the correct terminology. I’m not very well-versed in Shopify code. To do what I want, it seems like I would need to add the code to buy-buttons.liquid to make sure the note appears on relevant products in the cart page, as well as adding a Checkout UI extension so that the Final Sale note will be visible when customers go through the checkout.
Thanks again!
When customer adds a product variant to the cart it becomes a cart line item.
Line items may have properties added which will be passed into cart, checkout, order, etc.
This is not a “message in checkout”, but can be treated as one.
Modifying checkout can be tricky, especially if not on a Plus plan and would require an App.
Usually, there is no need to edit your theme code to add a line item property – this can be done using a “Custom liquid” block in “Product info” section of your product page template.
If you share your theme name or, better yet, a link to your store, we can suggest a code to do so.