> ## Documentation Index
> Fetch the complete documentation index at: https://baas-api-docs.rexmfbank.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Sandbox vs. Live

> How test and production environments differ on the Rex BaaS API

Your account has a single `environment` field — `sandbox` or `live` — set
with [Switch Environment](/api-reference/onboarding/switch-environment) and
readable from your [Login](/api-reference/authentication/log-in) response.
Every service call (creating accounts, transfers, transactions) operates
against whichever environment your account currently holds — there's no
separate sandbox/live API base URL to switch between for these calls, and
no separate credential per environment (see the token-lifetime caveat in
[Authentication](/authentication)).

## What's different in sandbox

* **Funding**: use [Fund Sandbox Balance](/api-reference/wallet/fund-your-sandbox-balance)
  to top your test business balance up to a working threshold — instantly,
  no real money involved. There's no live equivalent; a live balance is
  funded by real inbound transfers.
* **Interbank transfers to arbitrary accounts**: sandbox
  [Transfer Between Accounts](/api-reference/virtual-accounts/transfer-between-rex-issued-accounts)
  only supports Rex's own designated sandbox test accounts as a regular
  (non-Rex) beneficiary — sending to an arbitrary external account returns
  `400 REGULAR_ACCOUNT_NOT_SUPPORTED_IN_SANDBOX`. Transfers between two
  Rex-issued accounts work normally.
* **Rate limits, error shapes, and every other endpoint behave identically**
  in both environments — sandbox is not a stripped-down mock, it's the same
  code path against test data.

## Going live

You can't switch to `live` until your onboarding application is approved
(`onboarding_status: active`) — see the
[Going Live Checklist](/guides/going-live-checklist). Attempting to switch
earlier returns `403 NOT_ACTIVE`.

Once live, treat it exactly like production banking infrastructure,
because it is one: real transfers move real money and can't be undone the
way a sandbox mistake can.

## A note on `simulate-inward-credit`

You may notice
[Simulate Inward Credit](/api-reference/virtual-accounts/simulate-an-inward-credit)
in this reference and expect it to be the sandbox testing tool for inbound
transfers. It isn't reachable in production at all, for any partner,
regardless of your sandbox/live environment setting — it's gated to Rex's
own internal staging environment. To simulate money arriving in your
sandbox account, use
[Post a Manual Credit](/api-reference/virtual-accounts/post-a-manual-credit-or-debit)
or transfer from your funded sandbox Master balance instead.