Omission in books for Property Purchase Payment

I have a client who purchased a property during FY 2020-21. And the payment for the same are given in the past years(2015-2020). The value of the property is Rs.65,00,000 but in the books of client only 45,00,000 has being recorded. The sum of Rs. 20,00,000 did not get recorded in the books but has being paid by the client through bank in past years. How to rectify this ommission and difference in the books and match the ledger in this year. The client files the returns regularly.