Hi alison-finn,
We don't have a function to raise multiple, however if the invoices are the same and you just need to change a few details you can use the 'Copy' function by going to 'More' > 'Copy' on the invoice and then revise as needed.
You could also use the import data tool to import invoices using an excel file. You can import up to 1000 invoices at a time with this, all you need to do is download the sample file by going to the Gear icon > Import data > Invoices > Download a sample file and then over-write with your invoice details.
