TDS on payment of interest , other than interest on securities is governed by section 194 A of the Income Tax Act. Assuming ur client is an individual or a Hindu undivided family,
*whose total sales, gross receipts or turnover from the business or profession carried on by him exceed [one crore rupees in case of business or fifty lakh rupees in case of profession] during the financial year immediately preceding the financial year in which such interest is credited or paid, he/she shall be liable to deduct TDS under this section.
In this regard please note the following:
1) If the above* condition is satisfied, then he shall be liable to deduct TDS under section 194A, provided the interest amount exceed Rs. 5,000 in a financial year.
2) However if the status of your client is other than individual/HUF , then TDS has to be deducted irrespective of the turnover in the Previous FY, .
* My View.