Checkout is the narrowest part of any online store. Shoppers have already chosen their products, and the only thing left is to pay. Yet this is where many of them leave. Extra form fields, unclear shipping costs and unexpected steps all push people to abandon a purchase they had already decided to make.

BigCommerce gives merchants a good deal of control over this stage, but not unlimited control. Some parts can be adjusted in a few clicks, some need custom code, and some are deliberately locked for security reasons. Knowing where those lines fall saves time and prevents projects built on false assumptions.

Why Checkout Deserves Special Attention

A small improvement at checkout often has a bigger effect than a large improvement elsewhere. A shopper who reaches the payment step has already shown strong intent, so every point of friction costs real revenue.

The common causes of abandonment are well known. Many shoppers leave when forced to create an account, when extra costs appear late, when the form feels long or confusing, or when their preferred payment method is missing. Slow loading and a lack of trust signals add to the problem.

This is why it helps to treat checkout as its own project, with its own goals and measurements. Before changing anything, look at your data: where do shoppers drop off, on which devices, and in which regions? Changes based on evidence will always outperform changes based on opinion.

What You Can Change Without Touching Code

BigCommerce's built-in checkout, known as the Optimized One-Page Checkout, comes with a range of settings that need no development at all. These are the best place to start, since they are low risk and easy to reverse.

You can usually adjust which fields are collected, such as whether a phone number or company name is required. Guest checkout can be enabled so shoppers can buy without registering. Order comments, newsletter opt-ins and terms and conditions checkboxes can be switched on or off. Branding options, such as the logo, colours and fonts, let the checkout match the rest of the store.

Shipping and payment options are also configurable. You can control which delivery methods appear, how rates are shown and which payment gateways are offered. Settings for tax display, coupon codes and gift certificates are available as well.

When these settings are not enough, many merchants turn to BigCommerce development services to add custom logic around the checkout, such as special delivery rules, extra fields for B2B orders or connections to external systems. The sensible approach is to exhaust the built-in options first, then bring in development help only for what is genuinely missing.

The exact settings available depend on your plan and on the checkout version your store uses, and they change over time, so confirm the current options in the platform documentation.

What You Can Change With Custom Code

Beyond the settings, BigCommerce allows deeper customisation through code. This is where checkout can be shaped to match unusual business needs.

Custom scripts. On many plans, approved scripts can be added to the checkout to change its appearance or behaviour, for example to add tracking, adjust styling or display extra messages. These are powerful but need care, because a faulty script can break the page or slow it down.

The Checkout SDK and open-source checkout. BigCommerce provides tools that let developers build or modify the checkout interface directly. A development team can adapt the checkout code, change the layout of steps, add custom fields and connect them to other systems.

Custom fields and order data. Businesses often need to collect extra details at checkout, such as a purchase order number, a delivery instruction or a customer reference. These can be added and passed through to the order so the warehouse and finance teams see them.

Integrations. Checkout can be linked to tax engines, fraud tools, address validation services and loyalty systems. These calls happen during the purchase, so they need to be fast and reliable.

Conditional logic. Rules such as hiding certain shipping methods for specific products, adding a handling fee for heavy items or requiring approval for large orders can be built with custom development.

Each of these adds something to maintain. Keep a clear record of what was customised and why, and test the checkout after every platform update.

What You Cannot, or Should Not, Change

Some limits exist for good reasons, and it is better to know them before planning a design.

Payment details are protected. The fields where shoppers enter card information are handled by the payment provider or by secure components, not by your own code. This keeps sensitive data out of your store's reach and helps you meet payment security standards. You can style the surroundings, but you cannot capture or alter raw card data yourself.

Some platform behaviour is fixed. Certain parts of the standard checkout, such as the core order of steps or how some validations work, are controlled by the platform. If you need something far outside that structure, a fully custom checkout is usually the route, rather than trying to force the standard one to behave differently.

Third-party scripts have limits. Heavy or unreviewed scripts can be restricted or can cause conflicts, so adding many tracking tools at checkout is a risky habit. Every extra script is something that can slow the page or fail at the worst moment.

Legal and compliance rules still apply. Whatever the design, checkout must show required information, such as taxes, terms and consent options, according to the markets you sell in. Creative changes should never remove these.

Rather than treating these limits as obstacles, plan around them. A clean, standard checkout with a few well-chosen improvements often beats a heavily customised one that is hard to maintain.

Going Fully Custom With a Headless Checkout

Some businesses reach the point where the standard checkout, even with customisation, cannot deliver what they need. This often happens when the storefront is a custom build, or when the same checkout must serve a website, a mobile app and other channels.

In this case, a headless setup separates the shopping experience from the platform's back end. With headless commerce, developers build the checkout interface themselves while BigCommerce still handles the cart, taxes, shipping calculation and payment processing behind the scenes through its APIs.

The advantage is complete freedom over design and flow. The cost is responsibility: the team must build, test and maintain the checkout, including accessibility, security and performance. Many headless projects keep the platform's hosted checkout for the final payment step and customise everything before it, which balances flexibility with safety.

Choose this route only when the benefit is clear. If a conversion goal or a business requirement cannot be met by settings, scripts or the checkout tools, then going fully custom makes sense. Otherwise, the simpler option usually serves better.

Improvements That Usually Matter Most

Whatever level of customisation you choose, a handful of changes tend to deliver the most value.

• Offer guest checkout. Forcing registration is one of the most common reasons shoppers leave.
• Remove unnecessary fields. Ask only for what you need to deliver the order, and use address lookup where available.
• Show total costs early. Display shipping, taxes and fees as soon as possible, so the final price is never a surprise.
• Add the right payment methods. Match them to your audience and regions, including digital wallets where they are popular.
• Build trust. Show clear returns information, security badges and contact details near the payment step.
• Make it work on mobile. Large buttons, simple forms and quick loading matter most on small screens.
• Keep it fast. Remove scripts that are not needed and test load time regularly.
• Handle errors kindly. Clear messages that explain what went wrong, without clearing the form, keep shoppers from giving up.

Introduce changes one at a time where possible, and measure the result. If completion rates rise, keep the change. If not, you have learned something at a small cost.

Test and Maintain Your Checkout

Checkout deserves more testing than any other part of the store, because a fault here costs sales directly.

Test every payment method and every shipping option with real orders. Check discounts, gift certificates and tax calculations with a variety of baskets. Run through the process on several phones and browsers, and with a slow connection. Include unusual cases, such as international addresses, long names and orders with several promotions.

After launch, monitor completion rates, error reports and payment failures. A sudden change often points to a provider issue or a broken script. Re-test after every platform update, theme change or new app installation, since any of them can affect checkout without warning.

Finally, keep documentation. A short note listing every customisation, who built it and how to reverse it makes future changes far easier.

Conclusion

Checkout customisation on BigCommerce is a spectrum. Built-in settings cover most needs, custom code handles special requirements, and a headless approach offers full freedom when a business truly needs it. Some elements, especially payment data and core platform behaviour, stay protected for good reasons. Start with the simplest option that meets the goal, measure the effect, and add complexity only when the results justify it.