Wrong application of sec.44ad

Respected sirs, one of my client is having income from commission. while filing his IT return, i wrongly used 8% net profit provision.(sec.44AD) for which commission income is not eligible. 1) his income is below tax audit limit. 2) he now has received 143 (1) notice. 3) all the books are submitted to A.O what can be the sequence / penalty that can be imposed?