Do I still need to send an invoice when selling with Biller?

Biller buys the receivable, carries out the dunning/collection procedure for the seller and takes over the seller's accounts receivable for each purchased receivable. Once the purchase is confirmed by you, the seller, you should always send an invoice to the buyer. Biller will only take over the payment request. 

Please make sure to include your bank account details on this invoice to avoid buyers from paying you directly instead of Biller.