In theory, yes — worth knowing if you're planning a domain migration mid-flight. Idempotency keys sent to GoCardless for payment creation are built from the entry ID plus home_url() (e.g. pay-1234https://example.com), so GoCardless can recognise a retried request as a duplicate of one it already processed. If your site's URL changes between the original request and a retry — a domain migration, or switching http to https — the idempotency key changes too, and GoCardless will treat it as a brand-new request rather than a duplicate. This is a narrow window (it only matters for retries of in-flight payment creation, not for steady-state operation), but if you're cutting a domain over, it's worth doing during a quiet period rather than mid-signup-flow.