Property Tax

In March 2021 I purchased a resale flat. I came to know that builder as not submitted the completion certificate later on he submitted that the completion of building is done in the year 2018. So I have received a propert tax with my name for 4 years i.e from 2018 to 2022 but I am eligible for one year i.e 2022 and from whom I purchased the tax he needs to be paid tax for the year 2018 to 2021. So during the agreement I have asked my advocate to mention related to this like The Assignors have represented to the Assignee that they have paid outgoings electricity bills, maintenance charges etc. In respect of the said residential flat up to the date of execution of this Deed if Assignment The arrears of such outgoings and any other taxes/charges in respect of the dad flat for period prior to the date of execution of this Deed if Assignment, if claimed bt the Govt local authority or any other body, shall be paid by the Assignors and if at all paid by the Assignee the same shall be reimbursed by the Assignors to the Assignee. The Assignors shall indemnify or keep the Assignee indemnified of losses or damages caused to the Assignee due to their above -mentioned representation. Now he is denying to pay the property tax the above paragraph is from property agreement, what can de done in this case. Please assist me on this.