It filing u/s 143(1) a)

A time period of 30 days from the date of receiving the intimation is given to the recipient of the notice. If the recipient fails to respond, the return is processed after making necessary adjustment(s) u/s 143(1)(a), without providing any further opportunities in this matter.
Follow the following link to know the Procedure to Respond for notice u/s 143(1)(a)

https://help.myitreturn.com/hc/en-us/articles/115001711831-All-about-notice-u-s-143-1-a-and-how-to-deal-with-it