Missed out bill interest

SOWJANYA M (840 Points)

09 July 2020  
dear sir,

we missed out one February sale invoice while filing Feb returns
now gonna file march return ... if I add the missed invoice now, what will be the interest calculation if the tax is Rs.4000/-

4000*18%×111/365

no. of days correct??

Feb return due is mar 20, then 11 days in mar, 30 Apr, 31may, 30 June.....

is it like this?