Checkout
Take a customer from plan choice to paid with the fewest fields, a total that never surprises, and errors that keep what they typed.
8 states6 edge casesDesktop + Mobile
01The problem
Checkout is where intent turns into revenue, and every unnecessary field, surprise total or lost form costs paying customers. SaaS checkouts also carry business-specific complexity — tax IDs, VAT, seats, billing cycles, discount codes — that has to be handled without turning a two-minute task into a form-filling exercise.
02When to use
Use when
- Self-serve purchase of a plan or one-time product
- Upgrading from a trial or free plan to paid
- Buying add-ons or extra seats
Avoid when
- Enterprise deals with invoices and purchase orders — use a quote and invoice flow.
- The customer already has a saved payment method and is changing plans — use subscription management.
- App-store purchases, where the platform provides the checkout.
03Recommended UX
Statecraft recommendation
Show the order summary with the full total — including tax once the country is known — beside the payment form at all times, ask only for fields the payment or tax law requires, and keep everything the customer typed when payment fails.
04Desktop behaviour
On desktop, the payment form and the order summary sit side by side. The summary is the customer's anchor: it must always show the current total.
Desktop rules
- Order summary on the right with plan, seats, cycle, discount, tax and total — editable seats and cycle without leaving checkout.
- Put the total in the pay button: “Pay $948.19”.
- Collapse “Add discount code” and “Purchasing as a business” behind links.
- Show security and refund policy in one quiet line under the button, not as badges.
05Mobile behaviour
On mobile, the summary collapses to a total bar at the top so the form gets the screen, and wallet payments do most of the work.
Mobile rules
4 mobile rules are included in Pro.
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- Interaction flow · 6 steps
- 4 mobile rules
- 8 states
- 6 edge cases with recommendations
- 5 microcopy comparisons
- Accessibility notes
- Developer notes
- Claude Code / Codex implementation prompt
Edge cases covered in this pattern
- Card declined
- Tax changes the total
- Valid business tax ID
- Leaving for 3-D Secure
- Payment succeeded but the page failed
- Discount not valid for the selected plan