1) it would depend upon contract between parties .
2) if contract provides that in case of late payment by buyer interest would be charged at 18%pa then buyer has to pay said interest rate
3) contract would contain a provision that 30 days or 45 days be provided for making payment for goods sold and delivered
4) in case money is borrowed from money lender then money lender licence would be necessary .
5) if contract is silent about interest rate then seller would not be able to recover interest for late payments made
6) Section 194A deals with the provisions relating to TDS on interest other than on
securities. Tax is to be deducted under section 194A, if interest (other than interest on
securities) is paid to a resident.