How long must retailers keep receipts for items purchased from distributors and third parties? Is the retailer/distributor assumed to be guilty until they can show proof?

(Extreme example- do they need a receipt for the draft system a draft installer put in 30 years ago?)

1. Retailers must keep their receipts for 3 years and that distributors should carry the paid invoice for the same period. The same practice is recommended for third parties.
2. The burden is on the distributor and the retailer to show proof of ownership.  Golden Rule is both the retailer and the distributor should keep the receipt and the paid invoice as long as the retailer purchased the item