What a challan has to carry
The date, your details and the buyer's, the material with quantity and unit, the destination site, the vehicle number, the driver, the freight charge, and the name of whoever received it. Miss any of those and the document does not do its job on the day it is needed. All of it is captured on one screen while the truck is being loaded, and the challan links to the invoice it belongs to so the two are never separated.
Records that outlive the argument
Because the challan lives against the party rather than on a pad in a truck, it is retrievable years later and resendable on WhatsApp in one tap. When a contractor disputes a delivery you are not producing an amount, you are producing a document with a date, a vehicle number and his own man's name on it. Most disputes end at that point — and in material supply a single contested load is routinely several lakh, which is the whole economics of keeping the record properly.
One party, many sites
A builder buying from you across a dozen projects needs a ledger that can be read whole and site by site. Every delivery records the site it went to, so you can produce everything supplied to one tower or one address without going through three years of account. That is what settles the common argument, which is almost never about whether material was supplied but about which project it was supplied to.
Freight, and when a challan is the right document
The transport charge sits on its own line rather than being buried in the rate, so the customer sees what is material and what is delivery and your margin on the two stays visible. Under GST a delivery challan is the correct document where goods move without a completed sale — stock transfers, goods sent on approval, material moved to a job site. Where a load crosses the e-way bill threshold, the value, HSN codes and vehicle details are already recorded for the portal.