Urgent mvat query pending c forms

In a financial year, c form was pending to be received against one bill. This was reported in amnexure I by vat auditor. Now , the officer has issued notice demanding the pending forms. The dealer in another state issued c-form but the problem is : He has issued c-form for 120000 instead of 60000. This is because he has recorded the bill twice and also issued c form for twice the amount. Now how to solve this matter since only one sale was done. Should I pay differential tax with interest OR tell party to revise the same OR should I take letter from party saying there was only one sale bill and not 2 OR SHOULD I DEFEND BEFORE THE OFFICER THAT THE C-FORM IS RECEIVED FOR MORE THAN ACTUAL AMOUNT SO TAX LIABILITY IS ZERO ?