Redirect errors - Hosted checkout

TL;DR: Only a signed success return proves the URL wasn’t altered in the browser — and even then, that’s not proof a charge happened. Every other return carries no verifiable signal at all.

Params by outcome

Return	Params carried
Success, with a redirect secret configured	`checkout_id`, `state` (only if you sent one), `status`, `transaction_id`, `ts`, `sig`
Success, with no redirect secret configured	`checkout_id`, `state` (only if you sent one) — no `status`/`transaction_id`/`ts`/`sig`
Decline, failure, or manual back/close	Raw `cancel_url`, no params at all
Countdown timeout only	Raw `cancel_url?reason=timeout`
Rare: replaying a completion call on an already-terminal session	`success_url` or `cancel_url` with no params at all, even if a secret is configured

state is only ever present on a success return, and only if you sent one on create — it is never part of the signed payload (see below), so verify it independently if you rely on it for CSRF-style correlation.

Signature errors

Signal	Cause	What to do	Retry?
`sig` missing	No redirect secret is configured for your account (unsigned by design), or the secret was deleted	Confirm via webhook/`GET`; configure a redirect secret if you want the signed layer — see Verify the payment result	No — treat as unverified
`sig` present but doesn’t verify	The URL was altered in the browser, or you verified with the wrong key encoding	Check your HMAC key encoding first (see below); if it still fails, treat as unverified	No — treat as unverified
`ts` more than 5 minutes old	Merchant-enforced tolerance — RadiumOne itself doesn’t check `ts`	Reject the same as an invalid signature; this is your own server’s rule, not a gateway error	No — treat as unverified
Every signature fails, always	Wrong HMAC key encoding — the redirect signature’s key is the full `rsec_…` string, used directly. This differs from the webhook signature’s key, which is hex-decoded after stripping `whsec_`	Use the correct encoding for each signature type — see Verify the payment result	Fix first

Fail closed. If a redirect secret is configured for your account and a return is missing sig, has an invalid sig, or a stale ts — never treat it as confirmation of payment. See Reject invalid redirect signatures for the full walkthrough.

Next steps

Verify the payment result

The full trust hierarchy and redirect secret rotation semantics.

Reject invalid redirect signatures

Step-by-step handling for a missing or invalid signature.

Payment outcomes

What a decline, expiry, or cancellation looks like at the redirect layer.

API errors

Checkout API error codes for create/retrieve/cancel.

Introduction

Guides

3D Secure

Handle failures

Errors

Reference

Redirect errors - Hosted checkout

Params by outcome

Signature errors

Next steps

Verify the payment result

Reject invalid redirect signatures

Payment outcomes

API errors

​Params by outcome

​Signature errors

​Next steps

Verify the payment result

Reject invalid redirect signatures

Payment outcomes

API errors

Params by outcome

Signature errors

Next steps