Paul wrote...
....
I use Excel to summarize daily reporting into a monthly journal entry,
actually several of them. I have found cases where the formulas in the cells
do not calculate the correct results, which would cause the journal entry to
be incorrect. The formulas range from simple "If" statements to "DSUM" and
"SUMIF" formulas. I have not been able to find a solution to the problem
within my spreadsheets. The only explanation I can come up with is that
Excel is not working correctly.
....

Despite what you may believe, the odds are that any incorrect results
in your spreadsheets are the result of your own errors rather than
errors in Excel's internal functionality. There are exceptions, e.g.,
many of Excel's stats functions produce poor results for extreme (and
sometimes not so extreme) values, but for the most part Excel produces
the results it should given the restrictions on numeric precision.

If you're having problems with IF, SUMIF and DSUM, the problem is
likely either due to boolean comparison semantics you've misunderstood
or you have formulas that haven't been but need to be entered as array
formulas.

Without details it's impossible to diagnose your problem formulas.