Hi,
For the purpose of determination of value of supply under GST, Tax collected at source (TCS) under the provisions of the Income Tax Act, 1961 would not be includible as it is an interim levy not having the character of tax.
Corrigendum to Circular No. 76/50/2018-GST issued on 7th March 2019.
So, it would be tcs of 1% on INR 100 .