Advantage to the debtors.

[SueDonim]

what they really need is cash sale accounts for these folks that gives the good discount but requires payment at the time
(Not just a stupid loyalty card that might get you a free coffee once a week or a pittance off ).  Would seem to be a win win for everyone...  Do they exist?

Quite.

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That could be useful as a larger version of "loyalty" cards to prove that you are a regular customer, but doesn't really help to secure credit, other than giving someone a chance to build a relationship with a business. To change from cash to credit would still be a risk that requires some kind of credit history. When I was hit with this in 1980 I was told to go and get a credit card, which I did and therefore didn't need the hp I was asking for.

For OP's example no amount of loyalty cards will help to identify the person as a legitimate trade customer. That part is not about cash versus credit, but about whether you are bona fide when you don't have references from others in the trade.

I was not wanting credit.... they were happy to give me a discount so long as I had an account.,.. and fyi last time I dealt with a branch of that firm.. some years ago now in  one of many loads of timber I had 17 Tonne of palings delivered to me...

King1's suggestion is what you are wanting but I don't know of any system of "account" that isn't a credit account. Ultimately it still comes back to whether you qualify for trade supply or not. If it's just for your own build, they're unlikely to come to the party if you don't have "history".  The circle goes around.