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Checkout

Shopify checkout that follows your rules

Checkout UI extensions, Shopify Functions and Thank you page changes, built on Checkout Extensibility. Before we build anything, we tell you what your plan allows.

Discuss Your Project

The first call is free — 30 minutes. We reply within 1 working day.

Our Capabilities

Checkout changes that survive Shopify's updates.

  1. Checkout UI Extensions

    Extra fields, notices, upsell blocks and content in the information, shipping and payment steps. On Shopify Plus.

    0 - 1

  2. Discounts with Functions

    Tiered, bundle and customer-specific discounts that run inside Shopify's checkout, not in a theme script.

    0 - 2

  3. Payment & Delivery Rules

    Hide, rename or reorder payment and delivery options depending on the cart, the customer or the address.

    0 - 3

  4. Cart & Checkout Validation

    Order minimums, quantity limits and address checks that stop an order before it is placed, with a clear message.

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  5. Thank You & Order Status

    Surveys, delivery details and next steps after purchase, with extensions available on all plans except Starter.

    0 - 5

  6. Branding & One-Page Checkout

    Logo, colours, fonts and one-page or three-page layout in the checkout editor; deeper styling through the branding API on Plus.

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When We Can Help

Your checkout rules live in the wrong place.

  1. /01

    Old scripts stopped running

    Discount logic, shipping exceptions and payment rules that lived in Shopify Scripts or checkout.liquid no longer run. We rebuild the ones you still need as Functions and extensions.

  2. /02

    Checkout doesn't match how you sell

    B2B minimums, gift messages, delivery dates, order notes for made-to-order products: we add the fields and checks your orders need, inside Shopify's own checkout.

  3. /03

    Customers drop off at checkout

    Unexpected shipping costs, missing payment options, extra steps. We find what stops people at checkout, change it and measure what each change did.

Client Stories

What it’s like
to work with us.

Having partnered with Base X Tech for several years, they have become a highly trusted extension of our team. They deliver top-tier expertise across web development and platform integration.

VT AdvantecShopify Development
Discuss Your Project

How We Customise Checkout

From a list of rules to a checkout that applies them.

  1. Map & Check the Plan

    We list every checkout rule you have or need and mark which ones your Shopify plan allows.

  2. Choose the Tool

    A checkout setting, an App Store app, a Shopify Function or a UI extension: we pick the simplest one that does the job.

  3. Build & Test

    We build in a development store and test real carts: discount codes, markets, B2B customers and edge cases.

  4. Launch & Maintain

    We go live with your team, watch the first orders and keep the extensions current with Shopify's API versions.

Numbers that matter

* Average client rating on our Upwork agency profile.

What happens after launch matters more.

Your team

The team behind your project

Our team works across Kyiv, Lviv, Kraków and Spain, on CET hours.

FAQ

Questions
we get asked

What is Checkout Extensibility?

It is Shopify's current way to customise checkout. Checkout UI extensions change what customers see, Shopify Functions handle logic such as discounts and payment or delivery rules, and branding settings control the look. Customisations built this way are upgrade-safe, so Shopify can release checkout features without breaking them.

Do we need Shopify Plus to customise checkout?

For part of it. UI extensions in the information, shipping and payment steps, custom apps that contain Shopify Functions, and the branding API need Plus. Thank you and Order status page extensions work on all plans except Starter, and public App Store apps built on Functions can be used without Plus. We check your list of rules against your plan before quoting.

What can Shopify Functions do?

They run your own logic inside Shopify's checkout: product, order and shipping discounts, hiding or reordering payment and delivery options, cart and checkout validation, and bundles through cart transform. They took over what Shopify Scripts used to do. On Plus we build them as a custom app for your store.

Can you customise the Thank you and Order status pages?

Yes, with checkout UI extensions, which work on all plans except Starter. The old additional scripts field for these pages has been view-only since 28 August 2025, so tracking moves to web pixels and content moves to extensions.

We used checkout.liquid or Shopify Scripts. What now?

Both are retired. checkout.liquid stopped working for the information, shipping and payment steps on 13 August 2024, and for the Thank you and Order status pages on 28 August 2025 on Plus; other plans had to upgrade those pages by 26 August 2026. Shopify Scripts stopped running on 30 June 2026. We go through what the old code did and rebuild what still matters.

One-page or three-page checkout?

One-page is Shopify's default, and you can switch to three-page in Settings > Checkout. Customisations carry over when you switch. We check the header and the placement of each extension afterwards, because the one-page header is laid out differently.

Will a custom checkout improve conversion?

It can remove friction, but we don't promise a number. Each change gets a baseline and a measured result. If the problem starts before checkout, our conversion rate optimization work covers the whole funnel.

Should we use a checkout app or build one?

Start with what exists. Shopify's own Checkout Blocks app adds custom fields, payment and delivery rules and discounts without code on Plus, and content blocks on the Thank you and Order status pages on other plans. If your rules go beyond that, we build a custom app with Functions and extensions, which needs Plus.

Not sure what your plan allows?

Send us the checkout rules you need, and we'll tell you which ones work on your plan and how we would build them.

Discuss Your Project

The first call is free — 30 minutes. We reply within 1 working day.