First of all, SUMIF and SUMIFS have two different syntax.

SUMIF (range, criteria, [sum_range]) whereas SUMIFS (sum_range, criteria_range1, criteria1, ..., ...)

In your example, I would use SUMIFS...and assuming that "Billed Date" is on column A and "Paid Date" is on column B, and "Amount" is on column C, and that you only have 10 rows of data (from row 2 to row 11), then the formula would be

=SUMIFS($C$2:$C$10, $A$2:$A$10, "<>", $B$2:$B$10, "=")