You will not receive an invoice as a document/attachment, however, you will receive a payment confirmation.
If you decide to pay all in one term, you will receive a payment overview in your booking confirmation email.
If you have selected to pay in instalments, you will receive payment reminders where you can see the balance that is left to pay, and once you have completed the entire payment, you will receive a booking confirmation email. If necessary, you can use this confirmation as proof of successful payment.
You can also always find the payment overview by logging in to your Travel Bird account, under “Your Trips” in the “Payments” section.