Can the person chargeable with tax pay the amount of demand along-with interest before issue of notice under section 51B?

Yes. Before issue of notice under sub section (1) or a
statement under sub-section (2), a person chargeable with
tax, shall have an option to pay the amount of tax along
with interest and fifteen percent penalty, ascertained
either on his own or informed by the proper officer, and on
such payment, no notice shall be issued with respect to the
tax so paid.