Recurring Invoice - automatically put month/year in the description text

Recurring Invoice - automatically put month/year in the description text

Hello, 

how is it possible that in the description text of a recurring invoice always the actual month and year is defined? Our company provides permanent services that we invoice on a monthly basis. Our clients want of course have defined somewhere the month for which the invoice is issued. Only the date of invoice is not sufficient and in the short cuts there is only %InvoiceDate% what defines the full date and not only the month and year. 

Thank you for a solution or answer on that.

Cheers,
Günther