Linking ACH Accounts



In order to create ACH transactions, you will need to link an external account in our system. Doing so successfully will create an ACH-US node on our system which you will input on the Create ACH Transaction payload when you wish to send an ACH to the linked account.

There are two methods to link external accounts for ACH.

1. (Recommended) Bank Logins / Account Aggregation Product

You can make use of our Account Aggregation product to connect external bank accounts (as well as pull data from them). This verification method is near-instant and has lower returns risks compared to providing account and routing (AC/RT) numbers for linkage as it eliminates the risk of providing the wrong AC/RT numbers. It also provides a better user experience, as most users will more readily know bank account login information than AC/RT numbers. Consequently, using the Account Aggregation product is our recommended linkage method.

If HTTP code 202 is returned, that means that MFA (Multi-Factor Authentication) is required. Because there may be multiple MFA attempts in a row, please build your logic to always check for an HTTP code of 202 (which means another MFA attempt was sent). Cycle through MFA attempts in this way until the HTTP code is 200.

When a 200 HTTP code is returned, all bank accounts associated with the user's bank login credentials are automatically linked. In some cases, this will link to multiple accounts (e.g. checking and savings accounts). Please ask the user to designate the preferred ACH node (and delete extra nodes after the user selects the preferred node).

Once the account is linked an email notice will be sent to the email address listed for the bank account.

Bank Logins Sub-Resources

Submitting Another Vendor's Account Aggregation Data to Skip Micro-Deposits

If you would like to use an account aggregator outside of Synapse, you can still pass us that data to skip micro-deposits.

Before beginning this process, please verify that Bank Logins are supported on your Spec Sheet. Steps:

  1. Verify account with External Account Aggregator - Use an account aggregator to connect to a user's bank account with their online banking credentials.

  2. Pull customer data from the account aggregator - This includes account owner, address and other account information.

  3. Pull Transaction Data from the account aggregator

    • Please note that 3 months minimum of transaction data (e.g. transactions of an end user's data) is required to link with a 3rd party account aggregator
  4. Format the data from the account aggregator as shown in Link with External Account Aggregation. Designate negative values with "Debit" True or False (boolean).

  5. Send all data to us when you link the bank account with our Link with External Account Aggregation API call, which is in actuality our link with AC/RT but with an increased payload. Micro-deposits will not send if this data is supplied.

2. Account & Routing Numbers + Micro-Deposit Verification

To link any US bank without bank logins, manually submit the account/routing number. By default, the node will only receive CREDIT status. To receive CREDIT-AND-DEBIT status, verify the account with micro-deposits. Please be aware that it will take 1-2 business days for the micro-deposits to show up in the user's account.

Unlike external accounts linked via Bank Logins, the balance amount on the ACH-US node will stay at 0 in the response body because we don't receive balance information from the external account when connecting via AC/RT numbers. This means sending money to and from the ACH-US node will not change the balance.

You can use our call Verify Routing Number to check if a routing number is valid.

Micro-Deposit Verification Steps

1. Initiate Micro-Deposits

Micro-deposits are automatically initiated when a bank account is linked with Account/Routing Numbers (assuming the user's KYC is complete).

2. Check Bank Statement

Within 1-2 business days, the user will see two small transactions (less than $1 each) on their bank account statement.

3. Verify Micro-Deposit Amounts

The user must return to your application and submit the two micro-deposit amounts. If the amounts are correct, the node will receive CREDIT-AND-DEBIT status.

A successful response will return the node information with "allowed": "CREDIT-AND-DEBIT". If an incorrect amount was passed, the node will stay in "allowed": "CREDIT" and the node timeline will be updated with note": "Invalid Micro Deposit amounts attempted".


Incorrect Attempts

Do not try to guess micro deposit amounts. Nodes lock after 5 incorrect attempts. If the user has misplaced micro-deposits, we recommend Reinitiating Micro-Deposits.

Reinitiating Micro-Deposits

If a user cannot locate their micro-deposits, please reinitiate micro-deposits. Micro-deposits can only be reinitiated 2 more times after the node is created. See Reinitiate Micro-Deposits for more information.

If the node is locked for too many invalid attempts, please reach out to Synapse SupportSynapse Support - Help Center: | Customer Support Email : [email protected] | Customer Support Phone Number : +1 (415) 688-2943 | Customer Support Hours : Monday-Friday, 8:00am - 7:00pm PT with the node ID and the micro-deposit amounts so we can verify the amounts manually.


Link ACH Account Sub-Resources

Micro-Deposit Sub-Resources

Updated 2 months ago

Linking ACH Accounts


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