After finishing paying your affiliate, if you enabled the Export invoice feature, both you and your affiliate will be able to export the invoice for the paid referrals.
Go to Settings > Payments > Advance: Export invoice and switch it On to enable the feature.
After marking the referral order as paid, you can download the invoice via Payments tab > Paid > See transaction details > Download invoice:
The exported invoice will contain the following information: Invoice ID, Payment method, Payment information, Payment amount, Affiliate name and Referral details
Also, your affiliate can see the referral details and export invoice with the same information via Payments > Details (the magnifier icon) > Download Invoice: