Invoicing isn't dealt with via Tapfiliate.
However, you can easily link invoicing software to Tapfiliate in order to automate the invoicing process. You can automate the process using our triggers feature, or by linking Tapfiliate to a dedicated invoicing service using Zapier.
Tax W9 & 1099
If you PayPal to pay out your affiliates, PayPal will handle reporting for you.
You can read more about how PayPal manages this here.