https://help.tallysolutions.com/docs/td9rel54/td9/tally_developer_tools/auth_lib_sdk.htm

Authentication Library SDK

Tally Authentication Library SDK is the development kit to use Authentication Library. Tally Authentication Library enables partners to create applications that can run on mobiles and tablets, so that customers can connect to Tally.ERP 9 on the move. This library provides user authentication with the help of Tally.NET Server- the gateway to interact with Tally.ERP 9 application remotely. Apart from a host of services such as data synchronisation, remote data access, and SMS services that TSS (Tally Software Services) offers, partners can create mobile applications to interact with Tally.ERP 9 securely.

Auth Library SDK can be accessed from Tools menu.

Note : Refer to the section Authentication Library for the detailed explanation of Authentication Library and its functionality.