Getting 234C interest tax to pay, why?

Bunty (personal) (55 Points)

10 August 2021  

I sold some debt mutual fund units in April 2020. Got some capital gain from that transaction. I realized I should pay advance tax for that debt fund gain. So I paid advance tax in Jan 2021. Now today while filing return I am seeing some amount to pay under "Interest for deferment of advance tax (section 234C)".

Can someone explain why I am getting interest amount to pay?