Testing in the Sandbox


The Sandbox environment allows you to test the Dwolla API without any real-world impact, meaning that no real, personal identifying information or financial data is used and bank transfer processing does not run as it would in Production. Since dummy data is utilized in the Sandbox environment, Dwolla provides a way to simulate various test cases by providing either sentinel values that can be used when making API requests or buttons that trigger certain actions (e.g. simulate bank transfer processing).

  1. If you are new to application development with Dwolla, we recommend you review our Sandbox Setup Guide.

Testing Customers and Accounts

Access API - Manage Customers

The Sandbox Dashboard allows you to manage Customers, as well as transfers associated with the Customers that belong to your Sandbox account. Once your application has created its Customers, you can access the Sandbox Dashboard to validate that the request was recorded properly in our test environment.

Access API - Verified Customers

Simulate identity verification statuses

There are various reasons an Access API Verified Customer may have a status other than “verified” after the initial Customer creation. You will want your app to be prepared to handle these alternative statuses.

In production, Dwolla will place the Verified Customer in either the retry, document, verified, or suspended state of verification after an initial identity verification check. To simulate the various statuses in the Sandbox, submit either verified, retry, document, or suspended in the firstName parameter in order to create a new Verified Customer with that status. Reference the resource article on customer verification for more information on handling identity verification for Verified Customers.

Simulate document upload approved and failed events

If an Access API Verified Customer isn’t systematically identity-verified, the Customer may be placed in a document status and will require an identifying document to be uploaded and reviewed. Reference the customer verification resource article for acceptable forms of identifying documents for Verified Customers.

Since the document review process requires interaction from Dwolla, sample test documents can be uploaded in the Sandbox environment to simulate the customer_verification_document_approved and customer_verification_document_failed events. Right click on an image below and select “Save image as…”. Note: When saving an image, make sure to keep the size, format, and name of the image the same.

Sample document approved image

Image of document approved

Sample document failed image

Image of document failed

Transfer - Manage Accounts

Unlike the Access API, you are unable to programmatically create accounts from your application. Transfer accounts should be created via Dwolla’s OAuth account creation experience. Once the test accounts have been created, your application can facilitate a transfer of funds to, from, or between test accounts after authorization is obtained via OAuth.

Testing Funding Sources

Test bank account numbers

Dwolla requires a valid U.S. routing number and a random account number between 3-17 digits to add a bank account. For testing purposes, you can use the routing number 222222226 or refer to the list of routing numbers from the Federal Reserve Bank Services website.

Simulate IAV success and error scenarios in Sandbox

Dwolla’s Sandbox environment uses a fake service which allows you to simulate the end-user experience for adding and verifying a bank account within the IAV flow. The default “success” scenario is a happy path flow that includes: a single set of MFA questions, presentation of two valid accounts and one account without a routing number. Any text can be entered in the input fields to allow you to proceed through the IAV flow.

To help you test error scenarios, a flag and an option can be used in the first field (usually username or ID) for the bank you are trying authenticate. The remaining input fields in the flow can be any string of text, as we allow you to proceed through the flow regardless of the information entered. Use the following flag and option values to test various error scenarios:

FlagOptionUser-facing message
-eInvalidLoginPlease make sure your login or security information is correct.
-eAccountNotFoundSorry, we’re unable to find your {BANK NAME} account. Please try again or use a different account.
-eUnsupportedSiteSorry, that financial institution is not supported. If possible, please choose a different one or an alternative method for connecting your financial institution.
-eAlreadyLoggedInIf you’re currently logged in to your {BANK NAME} account, please log out and try again.
-eVisitSiteWe’re unable to process your information because the {BANK NAME} site is currently requiring additional action from you. Please resolve this, then try again.
-eUnavailableSiteSorry, there seem to be some technical difficulties while attempting to process your information. Please try again later.
Example IAV error scenario

Screenshot of IAV user facing error message

Test micro-deposit verification

If your application leverages the micro-deposit method of bank verification, Dwolla will transfer two deposits of less than $0.10 to your customer’s linked bank or credit union account after calling the API to initiate micro-deposits. Since the Sandbox environment doesn’t replicate any bank transfer processes, any two amounts below $0.10 will allow you to verify the funding source immediately.

Test micro-deposit failed verification attempts

When verifying a funding source using the micro-deposit method of bank verification, users are allowed three attempts to correctly input the two posted micro-deposit amounts. If the user fails to verify the two posted amounts on the third attempt, an event will be triggered and the funding source will not be verified using those micro-deposit amounts. To simulate the microdeposits_maxattempts or customer_microdeposits_maxattempts events in the Sandbox, use the amounts 0.09 and 0.09 when calling the API to verify micro-deposits. Reference the micro-deposit verification resource article for more information on handling failed verification attempts.

Testing Transfers

The Sandbox environment does not replicate any bank transfer processes, so a pending transfer will not clear or fail automatically after a few business days as it would in production. The transfer will simply remain in the pending state indefinitely.

Simulate bank transfer processing

There are two options available for processing or failing bank transfers in the Sandbox environment.

  • Option 1: your application will call the “sandbox-simulations” endpoint (referenced below) which will process or fail the last 500 bank transfers that occurred on the authorized application or Sandbox account.
  • Option 2 (Access API only): you’ll use the “Process bank transfers button” in the Sandbox Dashboard, which will process or fail the last 500 bank transfers that occurred on your Sandbox account or any Access API Customers you manage.
Transfer - Simulate bank transfer processing

When calling the “sandbox-simulations” endpoint to simulate bank transfer processing for Transfer Accounts, you’ll use the OAuth account access token which belongs to the Transfer CIP Verified account involved in the transaction.

Sandbox simulations request and response
Accept: application/vnd.dwolla.v1.hal+json
Content-Type: application/vnd.dwolla.v1.hal+json
Authorization: Bearer {Your access token}


  "_links": {
    "self": {
      "href": "",
      "type": "application/vnd.dwolla.v1.hal+json",
      "resource-type": "sandbox-simulation"
  "total": 8

Note: If a bank-to-bank transaction is initiated between two users, you’ll want to simulate bank transfer processing twice in order to process both sides of the transaction (debit and credit). Processing for bank transfers will also include initiated micro-deposits. If your application is subscribed to webhooks, notifications will be sent, including all transfer or micro-deposit related events, letting your application know that transfers have processed or failed.

Access API - Process bank transfers button

A “Process bank transfers” button is available in the Sandbox Dwolla Dashboard and Admin. This button performs the same function as the “sandbox-simulations” endpoint (mentioned above) and allows you to simulate bank transfer processing in the Sandbox. Once the button is clicked, Dwolla will process or fail (see below for how-to trigger ACH failures) the last 500 bank transfers that occurred on your Sandbox account or the Access API Customer accounts you manage.

Screenshot of process bank transfers button

Test bank transfer failures

Transfers to or from a bank account can fail for a number of reasons (e.g. insufficient funds, invalid account number, etc. ). When a bank transfer fails, the associated financial institution that rejected the transaction assigns an ACH return code and a transfer failure event is then triggered in Dwolla. Dwolla allows you to trigger various bank transfer failures by specifying an “R” code in the funding source name parameter when creating or updating a funding source for a Dwolla Account or Access API Customer. When a transfer is initiated using a funding source that has an “R” code assigned to its name, a transfer failure event will trigger and the status will update to failed when you simulate bank transfer processing (as mentioned above).

Dwolla allows you to pass in a few different sentinel values that are used to test different bank transfer failure scenarios. The list of available sentinel values cover the most common uses cases where ACH return codes can be triggered in production. Reference the list of codes in the following table:

Return codeDescription
R01Insufficient Funds: This value is used to simulate funds failing from the source bank account (ACH debit).
R03No Account/Unable to Locate Account: This value is primarily used to simulate funds failing to the destination bank account (ACH credit). The funding source will be automatically removed from Dwolla when this return code is triggered.
R01-lateThis value is used to simulate funds failing from the source bank account post-settlement. Note: You must click “Process bank transfers” twice in order to test this scenario.
R03-lateThis value is primarily used to simulate funds failing to the destination bank post-settlement. The funding source will be automatically removed from Dwolla when this return code is triggered. Note: You must click “Process bank transfers” twice in order to test this scenario.
Example of using a sentinel value for testing bank transfer failures

This example assumes that a funding source has already been attached to an account. Once the funding source name has been updated to reflect the ACH failure scenario you want to test, then you can initiate a transfer to or from that funding source via the API.

Accept: application/vnd.dwolla.v1.hal+json
Content-Type: application/vnd.dwolla.v1.hal+json
Authorization: Bearer pBA9fVDBEyYZCEsLf/wKehyh1RTpzjUj5KzIRfDi0wKTii7DqY


  "name": "R03"
funding_source_url = ''
request_body = {
      "name" => "R03",

# Using DwollaV2 - (Recommended)
funding_source = "#{funding_source_url}", request_body # => "R03"
 *  No example for this language yet. Coming soon.
funding_source_url = ''
request_body = {
  "name": "R03"

# Using dwollav2 - (Recommended)
funding_source ='funding-sources', request_body)
funding_source.body['name'] # => 'R03'
var fundingSourceUrl = '';
var requestBody = {
  name: "R03"

  .post(fundingSourceUrl, requestBody)
  .then(res =>; // => "R03"

Financial institutions play an important role in the Dwolla network.

Dwolla, Inc. is an agent of Veridian Credit Union and Compass Bank and all funds associated with your account in the Dwolla network are held in pooled accounts at Veridian Credit Union and Compass Bank. These funds are not eligible for individual insurance, including FDIC insurance and may not be eligible for share insurance by the National Credit Union Share Insurance Fund. Dwolla, Inc. is the operator of a software platform that communicates user instructions for funds transfers to Veridian Credit Union and Compass Bank.