VCI Sandbox will use https://api.sandbox.vericheck.com URL. The parameters and headers are the same for the sandbox requests and responses with a few changes defined in parameter definitions below. Specifically, Routing Numbers for Sandbox are limited to these values: 130000006, 140000009, 150000002, 160000005, 170000008, 180000001, 190000004

Sandbox returns are triggered based on the Description field of the current transaction being created. A description using the following format will trigger a return:
DayNRxx - where N is the number of days to trigger the return e.g. 1-9 days; xx is the return reason code where common return codes are:
R01 - NSF
R02 - Closed account
R03 - Account not found
R10 - Unauthorized
R29 - Corporate Unauthorized

Description field is Day2R03 will create a return for the transaction being created, after 2 days with the return code of R03.

Sandbox transactions will originate on the same day at 1800 (6pm ET).
Sandbox transaction will settle after 3 business days.