Split a large checkout epic into stories

The aim is stories that are vertical slices: each delivers a small piece of working value end to end (UI, logic, data), can be finished within a Sprint, and can be tested on its own. I avoid splitting by technical layer, such as "build the checkout database".

For a checkout epic I would begin with the thinnest complete path, a walking skeleton:

1. Guest pays for a cart with one card type and receives an order confirmation.
2. Validate card errors and show clear failure messages.
3. Add a second payment method, such as a digital wallet.
4. Add shipping options and cost calculation.
5. Apply discount codes.
6. Saved addresses and payment details for returning users.
7. Order confirmation email and order history.

Useful splitting patterns: by workflow step, by business rule variation, by data type, by happy path versus edge cases, and by simple versus complex.

Then I order the slices by value and risk, so the team learns early and stakeholders can see progress each Sprint.