There are certain situations where a company would like to factor a one time single invoice. This is commonly called “spot factoring.” It normally involves a significantly large invoice.
Most factoring companies will not do spot factoring due to it being a very risky transaction. It’s mainly because should there be a problem with the customer paying the invoice there’s little or no recourse available to seek repayment.
If you can find a factor willing to buy a single invoice, the first step would be to determine the creditworthiness of the customer who owes on the invoice. Unless they are a Fortune 100 company, who has bought from you before, it’s unlikely a factoring company will entertain this opportunity. Additionally the sales agreement or purchase has to be ironclad without any wiggle room.
Spot factoring is very tough to accomplish. As a factor I would be asking why you need it, as opposed to a longer ongoing funding relationship.