(k) any individual or a Hindu undivided family or an association of persons or a body of individuals, whether incorporated or not, other than those falling under any of the preceding clauses], whose total sales, gross receipts or turnover from the business or profession carried on by him exceed the monetary limits specified under clause (a) or clause (b) of section 44AB during the financial year immediately preceding the financial year in which such sum is credited or paid to the account of the contractor,
So, in the year when he actually reached the 40 Lkahs turnover , he may not be required to deduct the tax at source , but next year even if turnover is less than 40 Lakhs ,he is required to deduct the tax at source.
So, as far as , your question is concerned, no TDS is required to be made if the turnover in preceding year was not 40 lakhs. If it was,, assessee had to deduct the tax from beginning. There is no scope of confusion.