Dear Sir,
Issue in selling the land below circle value is that income tax department may replace the actual sales value with the circle rate and that will result into higher capital gain taxes.
You should challenge the stamp value of the property at the time of paying stamp duty. Also keep copy of those advertisement with you.
Whatever documents you have to show that actual market value of the property is lower than SDV, that you should maintain.
Please feel free to call/ revert in case of any doubts
Thanks and Regards
Abhishek Dugar
CA CS B.Com