how to set default for filter as

I have a tbl_invoices with field paid = 1 or 0 depending on if it is paid. This is setup to checkbox in phprunner.
I have setup paid: filter as Boolean and changed message to Paid / Unpaid.
All works well.
the thing I want to add is if it could show unpaid by DEFAULT and then the user can clear the filter to see all or switch between paid / unpaid.
Ultimately, they wanted a sub-menu that said paid/unpaid but I did not want to build an entire new view just for this... I think the filter solution will work if I can just get it to start out with unpaid.