Mr. Deepak
it is not compulsory to show 8% profit. if profits are less than 8% then audit is required. that is the provision.
generally no one wish to sell the goods at the price at which they bought.
There may be whatever the reason for selling at the same price or at lower price.
income tax depts expect some tax from you when you do business.
if you show no profit or even loss in your return of income, the department may suspect you that you are intentionally showing lessor profit or nil prfit or loss.
so, when you show lessor profit or loss, income tax dept requires you to get audit for correctness of profit or loss you have declared.
and when it comes to accounting.. there is no special accounting is required in your case. just book sales at the price at which you sell the goods i.e 15 lakhs. and book puchases at 15 lakhs. show profit nil. and get books audited.
i hope you are now clear with my explanation.