Unregistered assessee received SCN

Mohan Kale   22 January 2021

The assessee crossed basic exemption of ten lakh in FY 15-16 but did not take service tax registration. Now the SCN is received after preliminary submission of 26AS, ITR for the year. The tax calculation as per SCN is on whole turnover during the year.
1. Whether the assessee can be denied benefit of basic exemption of ten lakh in the year when he crosses the said exemption limit?
2. As the registration was not obtained in that year and in next FY there was turnover of less than basic exemption what defence assessee can take?