Create, list, and retrieve Returns — the reversal of settled payments such as ACH returns — on the Newline platform. Returns move funds back across the originating rail and update the associated Transfer and Transaction records, supporting exception handling in embedded payment programs at Fifth Third Bank.
Newline Returns API is one of 13 APIs that Fifth Third Bancorp publishes on the APIs.io network, described by a machine-readable OpenAPI specification.
Tagged areas include Returns, ACH, Payments, Exceptions, and United States. The published artifact set on APIs.io includes an OpenAPI specification and an API reference.
This API exposes
53 operations
across 40 paths,
organized into 13 resource areas.
It is described by OpenAPI 3.0.2, at version 1.0.0.
Requests are made against a single base URL, https://sandbox.newline53.com/api/v1.
53 operations40 paths0 schemas3 DELETE34 GET9 POST7 PUT
Metadata
The identity and technical contract details declared by the specification.
Specification
OpenAPI 3.0.2
API Version
1.0.0
Base URL
https://sandbox.newline53.com/api/v1
Authentication
API Key
Resource Areas
13
Authentication & Security 1
Newline Returns API declares
1 security scheme
for authenticating requests.
An API key is passed in the header as Authorization (ApiKeyAuth).
By default, every request must be authenticated.
ApiKeyAuth — Access token signed with shared HMAC
Paths & Operations 53
Across 40 paths, the API surfaces 53 operations — 3 DELETE, 34 GET, 9 POST, 7 PUT. They span 13 resource areas, including Auth, Customers, Pools, Products, Customer Products, Custodial Accounts, Synthetic Accounts, Transfers, and 5 more. Each is listed below with its method, path, parameters, and response codes.
Auth 1
The Authentication section explains how to securely interact with Newline's API using access tokens and static IP addresses. Learn how to generate and refresh tokens to access pro…
POST
/auth
Generate an authentication token
2 params→ 201
Customers 5
The Customers section provides details on managing end-user accounts. Learn how to create, update, and archive customer records and onboard them to financial products while meetin…
GET
/customers
Get a list of Customers
17 params→ 200
POST
/customers
Create a new Customer
1 parambody→ 201
GET
/customers/{uid}
Get a single Customer
2 params→ 200
PUT
/customers/{uid}
Adjust Customer Data
2 paramsbody→ 200
DELETE
/customers/{uid}
Archive a Customer
3 paramsbody→ 200
Pools 2
Pools group multiple Customers for asset sharing and distributed account ownership. Each Pool is unique to a Customer or program. Endpoints: - GET [List Pools: GET /pools](https:/…
GET
/pools
List Pools
4 params→ 200
GET
/pools/{uid}
Get a single Pool
2 params→ 200
Products 2
Products represent financial services available in your program. Discover onboarding requirements, prerequisites, and detailed product configurations. Endpoints: - GET [List Produ…
GET
/products
List Products
2 params→ 200
GET
/products/{uid}
Get a single Product
2 params→ 200
Customer Products 3
Customer Products link Customers to financial products. This section outlines how to onboard customers, manage their product relationships, and track statuses. Endpoints: - GET [L…
GET
/customer_products
List Customer Products
4 params→ 200
POST
/customer_products
Onboard Customer onto a Product
1 parambody→ 200422
GET
/customer_products/{uid}
Get a single Customer Product
2 params→ 200
Custodial Accounts 4
Fifth Third Bank holds Custodial Accounts and represents funds managed for Customers. Through these endpoints, you can manage balances and track account statuses. Endpoints: - GET…
GET
/custodial_accounts
List Custodial Accounts
7 params→ 200
GET
/custodial_accounts/{uid}
Get a single Custodial Account
2 params→ 200
GET
/custodial_account_closing_balances
List Custodial Account Closing Balances
8 params→ 200400500
GET
/custodial_account_closing_balances/{uid}
Get a single Custodial Account Closing Balance
2 params→ 200
Synthetic Accounts 9
Synthetic Accounts serve as the foundation for asset tracking in Newline. They allow for flexible configurations tailored to your program. Endpoints: - GET [List Synthetic Account…
GET
/synthetic_account_types
List Synthetic Account Types
4 params→ 200
GET
/synthetic_account_types/{uid}
Get a Single Synthetic Account Type
2 params→ 200
GET
/synthetic_accounts
List Synthetic Accounts
11 params→ 200
POST
/synthetic_accounts
Create a New Synthetic Account
1 parambody→ 201409
GET
/synthetic_accounts/{uid}
Get a single Synthetic Account
2 params→ 200
PUT
/synthetic_accounts/{uid}
Update the Synthetic Account metadata
2 paramsbody→ 200400
DELETE
/synthetic_accounts/{uid}
Archive a Synthetic Account
2 params→ 204422
GET
/synthetic_account_closing_balances
List Synthetic Account Closing Balances
8 params→ 200400500
GET
/synthetic_account_closing_balances/{uid}
Get a single Synthetic Account Closing Balance
2 params→ 200
Transfers 4
Transfers facilitate the movement of assets between accounts, enabling transactions such as payments and withdrawals. Endpoints: - GET [List Transfers: GET /transfers](https://dev…
GET
/transfers
List Transfers
8 params→ 200
POST
/transfers
Initiate a Transfer
1 parambody→ 201
GET
/transfers/{uid}
Get a single Transfer
2 params→ 200
PUT
/transfers/{uid}/cancel
Cancel a Transfer
2 paramsbody→ 200400422
Sandbox 1
The Sandbox section provides tools to test and simulate interactions with the Newline API in a controlled environment. Endpoints: - POST [Simulate a Transaction: POST /sandbox/moc…
POST
/sandbox/mock_transactions
Simulate a Transaction
1 parambody→ 201
Transactions 9
Transactions represent asset movements, such as ACH payments, wire transfers, or card purchases. Track transaction statuses and events through these endpoints. Endpoints: - GET [L…
GET
/transactions
List Transactions
26 params→ 200
GET
/transactions/{uid}
Get a single Transaction
2 params→ 200
PUT
/transactions/{uid}/authorize
Approve or deny a transaction
2 paramsbody→ 200400403422
GET
/transaction_events
List Transaction Events
9 params→ 200
GET
/transaction_events/{uid}
Get a single Transaction Event
2 params→ 200
GET
/synthetic_line_items
List Synthetic Line Items
9 params→ 200
GET
/synthetic_line_items/{uid}
Get a single Synthetic Line Item
2 params→ 200
GET
/custodial_line_items
List Custodial Line Items
11 params→ 200
GET
/custodial_line_items/{uid}
Get a single Custodial Line Item
2 params→ 200
Virtual Reference Numbers 7
VRNs act as aliases for accounts, enabling unique use cases like accounts receivable segmentation or reconciliation. Endpoints: - GET [List Virtual Reference Numbers: GET /virtual…
GET
/virtual_reference_numbers
List Virtual Reference Numbers
5 params→ 200422
POST
/virtual_reference_numbers
Create a new Virtual Reference Number
1 parambody→ 201422
GET
/virtual_reference_numbers/{uid}
Get a single Virtual Reference Number
2 params→ 200404
PUT
/virtual_reference_numbers/{uid}
Edit a Virtual Reference Number
2 paramsbody→ 200404422
DELETE
/virtual_reference_numbers/{uid}
Archive a single Virtual Reference Number
2 params→ 204404
PUT
/virtual_reference_numbers/{uid}/lock
Lock a single Virtual Reference Number
2 paramsbody→ 200404422
PUT
/virtual_reference_numbers/{uid}/unlock
Unlock a single Virtual Reference Number
2 params→ 200404422
Returns 3
The Returns endpoints help initiate, track, and manage returns of received and originated payments. These endpoints are accessible within the Sandbox and Production environments.…
GET
/returns
List Returns
3 params→ 200403422
POST
/returns
Create a new Return
1 parambody→ 201400403422
GET
/returns/{uid}
Get a single Return
2 params→ 200403404
Combined Transfers 3
The Combined Transfers endpoint allows clients to create both a transfer and a counterparty in a single API call. This simplifies the process by eliminating the need to first crea…
GET
/combined_transfers
List Combined Transfers
13 params→ 200403422
POST
/combined_transfers
Create a new Combined Transfer
1 parambody→ 201403422
GET
/combined_transfers/{uid}
Get a single Combined Transfer
2 params→ 200403404
Specification
The full machine-readable OpenAPI contract behind this narrative.
