Getting an invalid expression in my WF condition > formula. How should this be written?

Have you tried wrapping the fields in NVL? like so: CASE WHEN NVL({balance},0) + NVL({unbilledorders},0) > NLV({creditlimit},0) THEN 'TRUE' ELSE 'FALSE' END

Are all those fields the same data type? Maybe also try a to_nunber() for comparison

they are all string data type and i tried both suggestions (thanks) but still get the invalid expression error