Finding your NMI keys

Where each key lives in the NMI merchant portal and which permission it needs.

Sign in to your NMI merchant portal as the account owner or an administrator. Live accounts usually use secure.nmi.com/merchants, sandbox accounts sandbox.nmi.com/merchants, and many resellers have their own branded portal. Newer portals say Settings; older ones say Options.

Private security key (required)

1. Open Settings → Security Keys.
2. Click Add a New Private Key and name it after your website.
3. Tick the API permission (and Reports or Query if you see them).
4. Save and copy the key. Treat it like a password.

Public tokenization key (required for new cards)

1. On the same page, under Public Security Keys, click Add a New Public Key.
2. Choose the Tokenization permission and save.
3. Copy the key. It looks like six groups of letters and numbers with dashes.

Public checkout key (only for 3D Secure)

Most stores do not need this. Only if you turn on 3D Secure: ask your reseller to enable the 3-D Secure service, then add another public key with the Checkout permission. It must be different from the tokenization key.

Webhook signing key (recommended)

1. Open Settings → Webhooks and add a webhook.
2. Paste the address the setup assistant shows you and tick the transaction events, including chargebacks if listed.
3. Copy the signing key shown at the top of the Webhooks page.

If something is missing

• No Security Keys menu: your user is not an administrator. Ask the account owner or your reseller.
• “Authentication failed”: the key is for the other environment (live or sandbox), or API permission is not ticked.
• Card fields do not appear: the tokenization key is wrong, or the checkout key was pasted instead.