You are not alone who have been sent this notice. I too have received a similar communication from Centralized Processing Center (CPC), Bangalore.
This communication is is response to a recent clash between CAs and IT department. Income tax department has adjusted some tax payer's refund against old demands, but these tax payers have never been issued such demands in past. So IT department is sending these communication to avoid any further issue and to play it safe in future.
Now coming to the issue, in past they may not have full tracking of TDS deposited or self assessment challans, so there may be a difference in what you declared in IT return and what IT department tracked. So now they are sending notices to clear the pending issues.
You should now, write to assessing officer with return copy of assessment year (for which demand has been raised) along with form-16 (which shows TDS deduction) and challan for self-deposited income tax, if any. Also make sure that form-26AS correctly shows tax deposit. Check TDS deduction and income tax refund Online here.
You can check assessing office details from the notice, you have raised this demand. As soon as they are satisfied with your proofs, they will remove the demand against your name in their database.
If you don't clear out this issue with assessing officer, they will put this amount in pending receivables and will deduct from genuine refunds, if any, in future filed returns.
please mention the section mentioned in the notice. It may be like intimation U/S 143 of Income Tax Act.