It refund

Respected Sirs, I have file IT Return of my friend Salary Case. I forgotten to fill form 10B. In this notice received from IT for filling form 10b to get refund otherwise to pay may tax 3000approx. When I go to fill form 10b, I seen 26as where the employer Reduced the TDS amount from near about some 50000 to 38000. . I am asking my freind to received fresh form 16 from employer but the employer does not gives the form 16. Now what should i do in this case? Should I file revised return. In how many days should i file revised return. Please give reply as soon as possible. Thanking you Venkatesh