Invoice Total was not printing; I replaced the Subtotal Formula on the Total Field, this is a quickfix but will not add in the case were there is Tax. I suspect that the variable $V{TOTAL_TAXAMT} is not being passed corrrectly from the subreport which makes the formula fail.
Subtotal:
($V{TOTAL_LINENETAMT}!=null)?$P{NUMBERFORMAT}.format($V{TOTAL_LINENETAMT}):new String(" ")
Total:
($V{TOTAL_LINENETAMT}.add($V{TOTAL_TAXAMT})!=null)?$P{NUMBERFORMAT}.format($V{TOTAL_LINENETAMT}.add($V{TOTAL_TAXAMT})):new String(" ")