I rejected a voucher (invoice) in BearBuy. Will the supplier be automatically notified by BearBuy?

No, the supplier will not receive a notification that the voucher (invoice) was rejected. Invoices should only be rejected if the supplier has confirmed that the invoice is void and payment is no longer expected. Be sure to contact the supplier directly to communicate regarding the invoice. If there was a mistake on the invoice, ask the supplier to submit a corrected copy of the invoice with a new invoice number.