I find it easier to send them from the reports function - once you run the complete report for the period and then click on each subcontractor and send from there (still have to put the email address in manually - but I have a spreadsheet with them on that helps) BUT you must remember to use back to go back to the report then click on the next subcontractor ... I also make sure it is on landscape when I send the report (so the subcontractor can read it) ... 

Again not the best but the quickest work around I have found.

I have always sent CIS vouchers each month - but to send one at the end of the year which shows each month would be really good for some of our (less organised)  contractors !!!!!!