Job work procedure: time bound return and deemed supply rules require principals to track inputs and capital goods and maintain records. Section 143 permits a registered principal to send inputs or capital goods to a job worker without tax subject to prescribed intimation and conditions; inputs must be returned or supplied within one year and capital goods (excluding certain items) within three years. The principal must keep proper accounts and declare the job worker's premises as an additional place of business to supply from there, subject to specified exceptions. Deeming provisions treat failure to comply with the time limits as a supply by the principal on the date goods were sent. Waste and scrap may be supplied by the job worker if registered, otherwise by the principal.