First of all, your are not liable for Tax audit since your turnover is less than rupees 1 Crore(Rs.50 lakhs for Professionals). if your client is an individual or HUF or Firm(other than LLP) and opted for Presumptive Taxation u/s 44AD you need to show at least 8% of total turnover as Business Income (if transactions made through other than cash it is 6%).If not opted for Presumptive Taxation No need to maintain these Percentage as profit... Presumptive Taxation U/s 44AD is available upto 2 crores turnover.. so even if your client having turnover of more than 1 Crore but opted for Presumptive Taxation no need to get Tax Audit U/s 44AB and no need to maintain Books of accounts. it is the Special exemption available for Sec 44AD..