Hi Claire,

Thanks for using our Product Support Community.

The only way around this would be to set up 12 recurring invoices, one for each month. You can then recall the relevant invoice for the month you need.

I appreciate that this workaround isn’t ideal, therefore, you can log this as a suggestion to improve our Sage 50 Accounts software on our Ideas Community.

To log your idea select SAGE 50CLOUD ACCOUNTING and then New.

Once logged, we’ll be able to use your idea and help us to shape your Sage software. Other customers will also be able to vote on your idea.

I had this exact problem and after several years of trying to resolve this with Sage I now have a field in the header which states "service rental for x Month" based on the invoice date and a trigger in the global details box on the footer tab (It is one of the few fields which we do not use which can be set on a reoccurring invoice and it will be remembered AND can be added / taken off a live invoice). You could also use the consignment number for this purpose but we use that for another purpose.
It is crude as I am in no way trained to write these but it works for us. I hope it helps

INVOICE.GLOBAL_DETAILS="Monthly+"?"Service rental for " + DateTimeToFormattedString (Invoice.invoice_Date + Days (31), "MMMM yyyy") :
INVOICE.GLOBAL_DETAILS="Monthly-"?"Service rental for " + DateTimeToFormattedString (Invoice.invoice_Date - Days (31), "MMMM yyyy") : ""

Thanks so much Leon. I'll try this now and let you know how I get on.