Why do customers see "Variant can only be purchased with a selling plan" when adding to cart on Shopify?

If your customers are seeing this error on your Shopify storefront, don't worry - your Early Bird pre-order campaign is set up correctly. This is a theme compatibility issue, not a problem with the Early Bird app.

The error appears when a customer tries to add a pre-order item to their cart using a button that isn't your main product page form - things like a home page featured product section, a sticky add-to-cart bar, a Quick Add or Quick Shop button, or any other secondary "Add to Cart" shortcut your theme includes.

Why this happens

Early Bird uses Shopify's official Selling Plans & Purchase Options to run pre-orders (the same system Shopify uses for subscriptions). When a customer adds a pre-order item to cart, Shopify needs to receive selling plan information alongside that request.

Your main product page sends this information correctly. But secondary add-to-cart buttons like sticky bars, home page featured sections, and quick add popups, typically don't. They're not connected to the same product form, so they don't pass the selling plan along. Shopify then blocks the action and shows the error instead.

This is a Shopify and theme limitation, not something Early Bird controls.

Workarounds to consider

1. Replace the secondary "Add to Cart" button with a "View Product" button

This is the most reliable fix and requires no coding. Instead of letting customers add to cart from your home page or other sections, redirect them to your product page where the pre-order works correctly.

Best for: Stores with a featured product section on the home page and no developer on hand.

Steps (no coding required):

1. Go to Online Store > Themes and click Edit theme

2. Find the Featured product section in the left panel. Click the hide icon next to the Buy buttons block to hide it.

3. Click Add block and choose Link button from the list.

4. Click on the new Link button block to configure it. Set the link to point to your pre-order product.

5. Update the label to something like View Product or Shop Now and save.

To revert after your pre-order period ends:

1. Go back to Online Store > Themes > Edit theme
2. Unhide the Buy buttons block
3. Hide the Link button you added
4. The original Add to Cart button will reappear

2. Untick "Only sell this product with these purchase options"

In your Shopify product settings, scroll down to Purchase options and untick the Only sell this product with these purchase options checkbox.

This removes the block that causes the error, so customers can add the item to cart from anywhere on your site without seeing the message.

Best for: Stores that need a quick fix and don't mind customers being able to add the product to cart as a regular purchase outside the product page.

3. Ask your developer to connect secondary buttons to the main product form

If you have a developer available, a more seamless fix is to update your theme's secondary add-to-cart buttons to submit via the main product form. You can also add the class sseb__form    to your main product form to ensure Early Bird targets the correct one.

Best for: Stores with a developer who can make small theme code changes.

4. Switch to backorders instead of pre-orders

Backorders don't use Shopify's Selling Plans, so they're not affected by this theme compatibility issue. Customers can add backorder items to cart from anywhere on your site without errors.

Best for: Stores capturing full payment upfront, without a need for deposit functionality, who want the simplest setup.

Need help?

If you have questions about which approach fits your store, feel free to email us at support@shopside.com.au. We're happy to walk through your specific theme and setup.