Notice u/s 276 & 277 of income tax

Dear Friends, 

One of my colleague filled online ITR-1 for the the A.Y. 2013-14 and reduced salary by Rs. 100000/- in ITR and got refund of Rs. 21000/- approx. Now Assessing officer issued a notice and asked the reason for showing less salary in ITR comparing to Form-16 and asked why he should not take action u/s 276C(1) and 277 which having imprisonment of Minimum 3 months and Maximum 3 Years. Now what steps he can take to solve this issue kindly advise. Thanking you.