rent from commercial property

GST will be levied on commercial rental income beyond Rs 20 lakh.

if annual rental income from commercial property is less than 20lakhs then should calculate under the head "Income from house property"

is that said under income tax act

Yes ,under the head"Income from house property"

attn: Sunil, pls tell the relevant section

Income from house property in general is taxable under the head “Income from House property” in the hands of the owner. This applies to both residential as well as commercial property. The amount of rent received from such property which is known as “annual value” is taxable under this head after deductions.

property ,I assumed as house property and not a vacant land.