Hi Paul,
This formula is pretty confusing because I can't decipher which fields relate to what. I think though you may be overthinking the formula.
It looks like you are evaluating each month of the year individually. Instead of using nested IFs, have each month as a separate statement. Better yet, use a case statement like:
{PARTINV.IEQOH#} <> 0.00 And
Select {?Month}
Case 1: (({SUMPRT.IQA01} =0 and {SUMPRT.IQYER#} = {?Year})
and ({SUMPRT.IQA12} =0 and {SUMPRT.IQYER#} = {?Year}-1))
Case 2: ({SUMPRT.IQA01} =0 and {SUMPRT.IQA02} =0 )
and {SUMPRT.IQYER#} = {?Year}
Default: etc...;
Separating the months into a Case or independant IF should get you your results.
Thanks,
Brian