One party, read site by site
The argument with a contractor is almost never whether material was supplied. It is which project it was supplied to, and it surfaces months later when a site is being closed out. Every delivery records the site it went to, so a single ledger can be read whole or filtered to one address — you produce everything that went to one tower without going through three years of account. That distinction is worth more in this trade than any report.
Proof that survives the disagreement
The challan carries the date, vehicle number, driver, destination and the name of whoever received the load, and it stays against the party permanently rather than on a pad in the truck. When a delivery is questioned you are not producing an amount, you are producing a document with the contractor's own man's name on it, resendable on WhatsApp in one tap. Most disputes end there, and a single contested load in material supply is usually several lakh.
Credit that follows somebody else's payment cycle
A contractor pays when the builder pays him, which means your money is two steps away from the site. That is normal and manageable, but only if you can see the shape of it: how much is out, how old it is, and whether the ageing is getting worse month on month. Credit limits set in advance turn the decision to stop supplying into a system rule rather than a conversation at the counter, which is exactly where it should not happen.
Rates, quotations and running orders
Large supply usually starts as a quotation and turns into deliveries over weeks. The quotation converts to an invoice without re-entry, and one quotation can produce several staged bills as the material goes out. Rates agreed with a contractor are held against the party so a supervisor billing at the site charges the agreed price rather than the counter rate — which is the small leak that adds up fastest when someone else is doing the billing.