try checking for empty string ..from above error i think your fields are string type..

Local Timevar TOS := if isnull({Claim.loss_time}) or {Claim.loss_time}="" then time(0,0,0) else
time(rtrim({Claim.loss_time}));
Local Timevar TOI := if isnull({CustomTable.time_formatted}) or {CustomTable.time_formatted} = "" then time(0,0,0) else
time({CustomTable.time_formatted});
time(0,0,0) + ((TOS) - (TOI))

Jyothi

I just noticed that when I do (if isnull({Claim.loss_time}) or {Claim.loss_time}="" then time(0,0,0), it defaults the time to 12:00 which messes up my calculations. How can I fix this issue??