24 September 2013
You have not mentioned your state.
1)Issue a credit note for excess collection of differential tax, and claim the tax amount. Or
2) Issue a credit note for entire bill value and raise a fresh bill for correct rate of tax. Or
3) In your state what is the time limit or revising the return? If possible, after issuing credit note for diff tax, revise the April return with correct taxable turnover of 5% and claim the excess payment in your current month.