Shopify Checkout Customisation and Functions

Description

Service Shopify checkout customisation: what each plan allows

Shopify checkout is changed through four tools: the checkout editor for branding, Shopify Functions for discount, payment, delivery and validation rules, checkout UI extensions for extra fields and content, and pixels for tracking. Every plan gets branding, pixels and Functions from App Store apps. Custom Functions and changes to the main checkout steps need Shopify Plus.

Discuss a Shopify requirement Last updated 2 October 2026

What can be changed, by plan

Shopify's rules here change often. This table reflects Shopify's documentation as read on 2 October 2026.

Change

Tool

Basic, Grow, Advanced

Plus

Logo, colours, fonts, background on checkout, Thank you and Order status pages

Checkout and accounts editor

Yes

Deeper styling beyond the editor

Checkout Branding API

No

Apps on the Thank you and Order status pages

Eligible apps, placed in the editor

Extra fields, banners or content on the information, shipping and payment steps

Checkout UI extensions

Discount, payment, delivery and validation rules from an App Store app

Shopify Functions inside a public app

The same rules written for your store alone

Shopify Functions inside a custom app

Payment terms set by a rule

Payment Customization Function

Conversion tracking in checkout

App pixels and custom pixels

Two lines decide most projects. Checkout UI extensions for the information, shipping and payment steps are available only to Plus stores. And although stores on any plan can use App Store apps that contain Functions, only Plus stores can use custom apps that contain them.

What has been retired

Merchants who customised checkout some years ago often find that their changes have stopped working. As of October 2026:

checkout.liquid is unsupported for the information, shipping and payment steps.

Additional scripts for the Thank you and Order status pages were sunset on 28 August 2025, and the box in checkout settings has been view-only since then.

Script tags on those pages were sunset on 28 August 2025 for Plus stores and on 26 August 2026 for stores on other plans. That later date was also the deadline for non-Plus stores to upgrade their Thank you and Order status pages. Upgrading replaces the old pages and any customisations on them.

Shopify Scripts were deprecated on 30 June 2026. Scripts still published on that date were deactivated and no longer run.

If a discount that used to apply automatically has vanished, or purchase tracking fell after one of those dates, this is the likely cause. The fix is to rebuild the behaviour with the current tools: Scripts to Functions migration covers the first case, and pixels cover the second.

Checkout changes merchants ask for

This table shows how each request is built and what it needs. It is a guide to the platform, not a list of delivered projects.

Request

Built with

Plan needed

Hide cash on delivery above an order value, for certain pin codes or for flagged customers

Payment Customization Function (hide, rename, reorder)

Any plan through an App Store app; Plus for a custom rule

Show UPI first, rename a payment method

Same

Hide a shipping option for heavy carts, rename or sort delivery options

Delivery Customization Function

Tiered discounts, discounts by customer tag, discounts across products, order and shipping

Discount Function

Stop checkout below a minimum order, above a quantity limit, or when a required tax ID is missing

Cart and Checkout Validation Function

Sell several items as one bundle line

Cart Transform Function (merge and expand)

Same; overriding a line's price, title or image is limited to Plus and development stores

Gift message, delivery instructions or GSTIN field inside checkout

Checkout UI extension

The same field, without Plus

A field on the cart page saved as a cart attribute

Any plan

Trust badges, delivery promise or an offer inside checkout

Survey, reorder prompt or tracking widget after purchase

An app block on the Thank you or Order status page

Meta, Google or other conversion tracking

App pixel from the platform's app, or a custom pixel

A note on cash on delivery. In Shopify, COD is a manual payment method, and orders placed with it are marked unpaid until someone marks them paid. A Function can decide who is offered COD; it does not verify the order or collect the money. The guide to payments on Shopify in India covers the rest, and reducing COD returns covers the operational side.

Before commissioning a Function for discounts, check Shopify's built-in types. Amount off a product, a collection or an order, buy X get Y, and free shipping all exist as codes or automatic discounts, with no development.

What the tools cannot do

They run in an isolated sandbox and are limited to the components and APIs Shopify exposes.

They have no access to payment information or to the checkout page's HTML. A design that depends on moving Shopify's own fields around cannot be built.

Shopify Functions

A Function changes decisions, not appearance.

A store can have at most 25 active Functions of each of these kinds: discount, payment customisation, delivery customisation and validation. A cart transform is limited to one per app.

Discount Functions run at the same time and have no knowledge of each other, so two apps that both discount the same line need to be tested together.

For carts of up to 200 line items, a Function has a budget of 11 million instructions, 128 kB of input and 20 kB of output. Rules that loop over large lists must be written with that in mind.

A Function generally cannot call your server while it runs. Network access has to be enabled by Shopify and is documented for only a few Function types, mostly for enterprise stores. Data a rule needs, such as a pin code list, is stored in metafields ahead of time.

Pixels

Pixels run in a sandbox, loaded by Shopify on the storefront, checkout, Thank you and Order status pages. They are managed under Customer events in the admin. A tracking snippet written for the old additional scripts box has to be rewritten as a pixel, not pasted across.

How WavX approaches a checkout change

Write the rule and find its tool. Each request maps to one row of the table above. If it maps to none, WavX says so at this point.

Check the plan. If the store is not on Plus and the request needs a checkout UI extension or a custom Function, the options are an App Store app, a cart-page alternative, or leaving it. WavX lays out all three.

Check for an existing app. For common rules, such as hiding COD by order value, a maintained App Store app is usually the cheaper answer.

Build in a development store. Functions and extensions are developed with Shopify CLI inside a custom app , with the rule's values (thresholds, pin code lists, customer tags) editable by the merchant from the admin.

Test the combinations. Every payment method, every shipping zone, a discount code on top of an automatic discount, a COD order, a draft order, and an express checkout button. Checkout rules fail at the intersections.

Release at a quiet hour, with a way back. Each rule is built so that it can be switched off without a new deployment, and the merchant is shown how.

When not to customise checkout

The change is cosmetic and the editor already does it. Logo, colours and fonts need no developer.

An App Store app has the rule. On Basic, Grow or Advanced it is the only route for checkout logic, and on Plus it may still be cheaper than a build.

The goal is a higher conversion rate and nothing has been measured. Shopify's checkout is the same one shoppers have used on other stores. Changes to it should follow evidence from the store's own funnel, which is conversion optimisation work, and no particular lift can be promised.

The only reason to move to Plus is one field. Plus is listed from ₹1,75,000 a month on Shopify's India pricing page as of October 2026. A gift note or a GSTIN field can usually be captured in the cart on any plan.

Custom checkout work is justified when a rule protects margin or reduces failed deliveries every day, when a retired script has to be replaced, or when a B2B flow needs terms and validation that no App Store app provides.

Cost

WavX does not publish a fixed price for checkout work. It is quoted after scoping, because a single Function with one rule and a set of extensions with their own admin screens are very different jobs. Functions and extensions are delivered inside an app, so the Shopify app development cost guide is the closest published reference. Other requests that touch the cart and product pages are covered under custom Shopify features .

Frequently asked questions

Can I customise Shopify checkout without Shopify Plus?

Partly. On Basic, Grow and Advanced you can brand the checkout in the editor, use App Store apps that contain Shopify Functions for discount, payment and delivery rules, add eligible apps to the Thank you and Order status pages, and track with pixels. You cannot add your own fields or content to the information, shipping and payment steps.

What is a Shopify Function?

A small program that runs on Shopify's servers at a fixed point in checkout and returns a decision: which discount applies, which payment methods to show, which delivery options to offer, or whether the order may proceed. It changes the logic of checkout, not its appearance.

Our old checkout scripts and tracking codes stopped working. Why?

Shopify has retired the older methods. Shopify Scripts were deprecated on 30 June 2026 and any published scripts were deactivated. The additional scripts box for the Thank you and Order status pages became view-only on 28 August 2025. The replacements are Functions, pixels and app blocks.

Can you hide cash on delivery for some orders?

Yes, with a Payment Customization Function, which can hide, rename or reorder payment methods based on the cart, the address or the customer. On Plus this can be a custom app with your exact rule. On other plans it has to come from an App Store app that offers the rule you need.

Should we upgrade to Plus just to change the checkout?

Rarely for one change. Plus is listed from ₹1,75,000 a month on Shopify's India pricing page as of October 2026, so a single extra field does not justify it. Check first whether the same result is possible in the cart or on the Thank you page.

Sources

Shopify Help Center: Customising checkout (features by plan) · read 2 October 2026

Shopify Help Center: Checkout extensibility · read 2 October 2026

Shopify developer docs: Checkout UI extensions · read 2 October 2026

Shopify developer docs: Build for checkout (deprecation notice) · read 2 October 2026

Shopify Help Center: Upgrading the Thank you and Order status pages · read 2 October 2026

Shopify Help Center: Shopify Scripts and the Script Editor · read 2 October 2026

Shopify developer docs: About Shopify Functions (plan availability) · read 2 October 2026

Shopify developer docs: Function APIs reference and limits · read 2 October 2026

Shopify developer docs: Network access for Shopify Functions · read 2 October 2026

Shopify developer docs: Payment Customization Function API · read 2 October 2026

Shopify developer docs: Delivery Customization Function API · read 2 October 2026

Shopify developer docs: Discount Function API · read 2 October 2026

Shopify developer docs: Cart and Checkout Validation Function API · read 2 October 2026

Shopify developer docs: Cart Transform Function API · read 2 October 2026

Shopify Help Center: Pixels overview · read 2 October 2026

Shopify developer docs: Cart Ajax API reference · read 2 October 2026

Shopify Help Center: Manual payment methods · read 2 October 2026

Shopify Help Center: Discount types · read 2 October 2026

Shopify India pricing · read 2 October 2026

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