Know what you can and cannot change
The checkout editor covers brand styling on every plan. Extensions add content into fixed slots, above or below the summary, near the delivery section or on the thank you and order status pages. The step order, field logic and page layout stay Shopify’s.
That constraint is a feature. Shopify tests its checkout across millions of orders, and it converts better than almost anything an agency would build. Spend the effort on the pages before checkout where you actually control the outcome.
Migrate anything still living in old scripts
If your store carried checkout.liquid customisations or entries in the additional scripts box, those stopped running. Tracking pixels move to custom pixels under Settings then Customer events. Order confirmation logic moves to Flow or an app. Line item discount rules move to Shopify Functions.
Audit this even if you migrated already. Silent gaps are common, especially conversion tracking on the thank you page and any third party script that quietly disappeared. Place a test order and confirm every downstream system receives it.
Spend on payments and delivery options instead
The two settings that move checkout completion are the payment methods offered and the delivery choices shown. Shop Pay, Apple Pay, Google Pay, PayPal and a buy now pay later option cover most UK expectations. Klarna and Clearpay matter in fashion and higher ticket categories.
On delivery, name the carrier and the arrival date instead of a generic standard label. Add a nominated day or a click and collect option if your operation supports it. Both reduce the last hesitation better than any checkout banner.