There must be clause in your sale  deed that seller indemnified you in case any claims are made 

2) for period 2001-2011 any revision has to be paid by seller 

3) contact the seller as to whether said flat was given on rent for period of 10 years prior to sale of flat to you 

Govt revenue does not become time barred. 

If any tax is due against  any property the present owner shall be held liable to pay such dues. 

However if the dues pertain to the period of previous owner you can claim it from the concerned previous owner, in default you can file suit in civil court for recovery of the money from the previous owner. 

You can file criminal case if it is prima facie evident that the person knowingly hide the fact of arrear of tax at the time of sale. 

You can seek evidence from them through documents to prove the rent factor. Also clarification to seek service of the same so delayed

File an affidavit of seller that property was never given on rent during period 2001-11 

also file detailed reply that after purchase of flat it has it has never been given on rent 

As per the Kolkata Municipal Act an assesse gets first opportunity to challenge the assessment before the Hearing Officer and thereafter before the Municipal Assessment Tribunal.

The order passed in MAT can further be assailed before the High Court as well.

So you have ample opportunity to defend your case and place necessary evidences to buttress the claim of tenancy alleged by the KMC. 

The previous owner may not be telling the truth. engage a lawyer who shall reply to the notice of payment and find out the details of the property and whether it was on rent and reply appropriately to the municipal council. He can also file an appeal in case of any adverse order.

Regards 

The owner has to state this on oath or affidavit that it was not on rent. 

1. Such disputes about past Claims can be settled ONLY in a Civil Court, where you can file and obtain Stay order in the matter. Further the authorities may be directed to produce evidence of premises being on rent etc.... and declaring the claim as infructuous under the Limitation Act.

Dear

You are not liable to pay any dues for mistake of municipality you should go for hearing and give your representation that you have purchased the flat in 2001 and since then you are residing in that flat and flat is not given on rent. 

And you have transferred the record by taking NOC from mutation department and updated the records after NOC.

need to go through the notice so that proper advice can be made in regards. pl contact local lawyer. 

Upon receiving the notice, you may consult a local advocate and issue a reply notice denying the liabilities that have been made against you by the authorities concerned.

You can mention all the details of your purchase and claim exemption on the grounds that you cannot be held liable for the past taxes, if at all they may have to levy the same, then they can do it only on the previous owners and not on you. 

You can prefer an appeal before the taxation appellate tribunal against the aggrieved orders, let the tribunal decide on merits.

You may even demand the evidences of the property let out on rent in the past in your reply notice.

1. As per the information mentioned in the present query, makes it clear that the Municipal authority can’t take the help of his own fault.
2. They should have given the notice much prior to the period so lapsed.
3. There is a limitation period for every claim, no body can wake up after so many years and ask for the money.
4. You need not to worry about their action, just appear and give reply in legal language to them.
5. If still creates problem then approach the Hon’ble HC for action against them only.