Stwrongly deposited

Kindly help me in following issue:-

The Individual had constructed the property and given it on rent in this Financial Year.

The Individual unknowingly has deposited online the ST Amount without realizing the same and also without availing the 10Lac exemption.

Now, the issue which has arisen is that now how to avail the exemption benefit and also to rectify the challans. Moreover, the tenant is also deterrent in paying the ST in the first 10Lac.

Thanking you in anticipation