IS 4926:2003 is the Bureau of Indian Standards' code of practice for ready-mix concrete. It sets out expectations across the full lifecycle of a batch — from raw material storage and batching accuracy, through transportation and delivery, to the checks that should happen on site before a pour is accepted.
For a buyer, the practical takeaway is this: a supplier working to IS 4926:2003 should be able to show you documentation for mix design, batching records, and the tests run on each batch. If a supplier can't produce that paperwork on request, that's a fair reason to ask more questions before you order.