Intimation under section 143(1) of income tax

Hello,

I have received a notification under 143(1) of IT act stating that some additional tax needs to be paid. When we filed TDS ,we filed with correct income, and also the form 16 and ITR filed is of the same amount.

But the income tax letter states that the income is more than what we have filed.

I just want to know how the IT department took the total income figure ?

Let me know what should i do to solve this problem ?