What should I do if CA has filed incorrect income tax return

Hi,

I have asked one CA for ITR in which I also asked him to add HRA and some other allowenace which I have not declaried at the start of the year. He has done it but he did mistake in the calculation of HRA. As per my understanding HRA calculation requried Basic Salary. But CA used whole month salary for HRA calculation. Which leads to wrong ITR filing and I was supposed to loss money but I saw this on time and told him. He said that he will rectify it but for the rectification, he is asking additional 1000 rs.

I already paid his fee which was1250 rs. Now He is saying that he will do the rectification only if I will give extra 1000 rs. I explained him that I am asking you to correct the mistake which you did and on this node he is not giving any response. I was surprised that how CA can do such a silly mistake while calculating HRA and he might did incorrect calcualtion with others as well and this may lead wrong immpression among tax payers. Please help me what action I can do on this situation.

Thanks for reading.