Unified KYC

Meld is working towards unifying KYC, so that a user only has to KYC once and then can use multiple onramps without having to KYC again.

In this flow, the user can go straight from your wallet to the payment screen of the onramp, skipping both logging into the onramp as well as KYC. Currently this flow only works if you KYC the user via Sumsub and send them to the onramp Mercuryo, although Meld will be adding support for more onramps shortly.

To enable this flow, do the following:

Step 1: KYC the user via Sumsub

This requires you to integrate Sumsub, and use them to KYC your user. Meld is working on an enhancement to return you a Sumsub KYC link via API that you can launch from your UI to KYC the user, which is coming Q1 2026.

In order for your user to not be asked for any additional KYC information by the onramp, you must collect, at minimum,

First name
Last name
Date of birth
ID picture
Phone number
Email address
Address
Country

You will have to fetch the KYC token of the user from Sumsub.

Step 2: Create a Meld customer

This step is required for the user to skip logging into the onramp, and is a one time setup per user. Call Meld's create customer endpoint, and pass in the user's first name, last name, email address, phone number, and birthday. Your request will look like this:

{
  "name": {
    "firstName": "First",
    "lastName": "Last"
  },
  "email": "[email protected]",
  "birthday": "01-30-1980",
  "phone": "+1-111-222-3456",
  "externalId": "testUser1"  // optional, for you to pass in your own reference id for the user
}

The response body will look like this:

{
  "name": {
    "firstName": "First",
    "lastName": "Last"
  },
  "email": "[email protected]",
  "birthday": "01-30-1980",
  "phone": "+1-111-222-3456",
  "externalId": "testUser1",
  "id": "W912345678", // customerId to pass into /widget
  "key": "N/A",
  "accountId": "W932jkkjn2jnjn",
  "addresses": {},
  "serviceProviderCustomers": {},
  "subAccountId": "N/A"
}

The id in the response is now the Meld customerId of that user. You will need to pass this to Meld every time that user wants to make a transaction.

Step 3: Pass Meld the KYC token

If you send the user to an onramp that support Sumsub token sharing, then pass Meld the KYC token of the user when you call Meld's /widget endpoint. Your request will look like this:

{
  "sessionData": {
    "countryCode": "US",
    "destinationCurrencyCode": "BTC",
    "serviceProvider": "MERCURYO",
    "sourceAmount": "100",
    "sourceCurrencyCode": "USD",
    "walletAddress": "1EEo4ioA4spdJ2ZxiSQ1hWsp3Ve81ZRZ2F",
    "kycInfo": {                      // optional field
        "kycProvider": "SUMSUB",
        "kycToken": "abcdefgh"        // the Sumsub KYC token for the user
    },
    "sessionType": "BUY",
    "customerId": "W912345678"        // should be the same as the customer created above
}

The response will look like this:

{
  "id": "WmYtVn52MCZkXQSdCFDU8N",
  "externalSessionId": null,
  "externalCustomerId": null,
  "customerId": "WmYtVoa7bdzxJAT5ygt91s",
  "widgetUrl": "https://meldcrypto.com?token=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ7.eyJpc3MiOiJtZWxkLmlvIiwiaWF0IjoxNzcxMjY3MDM4LCJzdWIiOiJjcnlwdG8iLCJleHAiOjE3NzEyNjg4MzgsImFjY291bnRJZCI6Ilc5a2c5aVAxc2JweVpwdFFEY0NNSnUiLCJzZXNzaW9uSWQiOiJXbVl0Vm41Mk1DWmtYUVNkQ0ZEVThOIn0.eqFYseggwUyv-F7WyO-LKEhwEqLiWVOmAV4lNjuth60",
  "serviceProviderWidgetUrl": "https://exchange.mercuryo.io?widget_id=34c04adf-d04a-42de-a4aa-609a302b24tz&currency=BTC&fiat_currency=USD&fiat_amount=100&address=1EEo4ioA4spdJ2ZxiSQ1hWsp3Ve81ZRZ2F&type=buy&network=BITCOIN&merchant_transaction_id=WmYtVmRXgDnavemEzb3k6K&redirect_url=https%3A%2F%2Fmeldcrypto.com&country_code=US&email&payment_method=card&signature=zxcvbnmasdfghjkl",
  "token": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJtZWxkLmlvIiwiaWF0IjoxNzcxMjY3MDM4LCJzdWIiOiJjcnlwdG8iLCJleHAiOjE3NzEyNjg4MzgsImFjY291bnRJZCI6Ilc5a2c5aVAxc2JweVpwdFFEY0NNSnUiLCJzZXNzaW9uSWQiOiJXbVl0Vm41Mk1DWmtYUVNkQ0ZEVThOIn0.eqFYseggwUyv-F7WyO-LKEhwEqLiWVOmAV4lNjuth60"
}

If you executed every step correctly, then when you open either the widgetUrl or serviceProviderWidgetUrl, then the user go straight to the Mercuryo payment screen, as seen in this demo video:

And that's it! Congrats, you are now using Meld's Unified KYC product to enhance your users' experience!