Factoring foreign receivables is a specialty service. Selling invoices due from foreign companies or governments is done by factoring companies that have the ability to do the documentation, underwriting and follow up on a transaction. International accounts receivable financing is done regularly everyday. But the factoring company doing the work usually concentrates solely on this kind of funding.
Unfortunately there is a significant barrier to entry for this financing. For the most part, invoice factoring companies financing foreign receivables will only work with a business producing a minimum of $100K of invoices monthly. In order for it to be worthwhile, this amount of billing is a starting point for getting funded. The amount of effort involved makes it unlikely to get smaller monthly amounts funded. So companies needing to do invoice factoring internationally might have to look to other resources when just starting out.