You cannot send invoices to Fairlingo. Instead you can download a creditinvoice for your bookkeeping if necessary.
1: Login at Fairlingo and go to "profile and settings" figure 1
2: Go to " credit invoices" figure 2
3: If necessary Update your payment details at "account settings" figure 3
4: You can download the creditinvoice at "invoices" figure 2. Please read the note below.
Fairlingo updates the invoices every first day of a new month. So after filling in your payment details and finishing an order, your invoice will be created on the first day of the following month.