Can I import external data into Recurring Invoices?

We do not have an official import tool for recurring invoices. That being said, since Recurring Invoice tables are just normal UDO Tables it should be possible to do using SAP Data Transfer Workbench.

Problem using this tool is since DTW can't apply recurring Invoice's business rules you manually need to make sure all rules are kept in the DTW run (Example that invoice run date needs to be between 1 and 31 and the stored totals need to be correct).

So technically possible but test a lot and at own risk if data becomes corrupt.