Need help with IF + CONCATENATE formula

I have a tracking spreadsheet for projects and I’m trying to use Concatenate to specify the quarter and year when a project was completed, but leave cells blank if I haven’t entered a currency conversion based on an invoice posting date. The formula works to determine quarter and year for the completed items, but I keep getting a “One of the parameters is invalid” error on the blanks where a project is either active/quoted and has no posting date or associated currency conversion.

IF({USD/CAD - Posting Date}="","",CONCATENATE(“Q”,ROUNDUP(MONTH({Posting Date})/3,0)," ",YEAR({Posting Date})))

Any thoughts on how to fix this or be able to drive it from a date or status column instead?