Income tax

I have filed ITR4 for one of my client and i have shown some business expenses under other expenses column due to lack of column of that particular expense. Now I received a intimation u/s 143 in which AO has disallowed that expenses and charged tax on that expenses. 

What procedure now I have to follow?

Whether I have to file revised return or to meet AO?

Pls reply asap.

Thanxs in advance.