Any allowance given to the employees based on the organization operating model to facilitate in performing the duties for a job well done by enhancing the speed is a custom allowance / miscellaneous allowance.
OfficePortal has configured a custom allowance as a key/ gateway to create multiple additional allowances as per the user’s desire. i.e., if you found the default allowance available in the portal does not match your requirement then you can add a new allowance by using the custom allowance.