Property tax assessment — Property tax assessment by chennai (pallikaranai) town panchayat

Sir, I moved to my newly built house 1 year back in pallikaranai chennai. I would like to pay property tax for my house. I have applied for property tax assessment with panchayat office thro registered post with acknowledgement with all the necessary document a month back. They are not ready to complete assessment without paying Rs.5000 as bribe. As I have not paid last year tax, I am ready to pay the tax dues with the penalty. They are saying that my building plan approval is expired and I have to get fresh building plan approval. I am about to file RTI application to know the status on my property tax assessment application. please guide me