This is a sample report Group by Customer. I'm calculating the balance value as:
Fields!Bill.Value-SUM(Fields!Paid.Value)
How to display balance Column as 0 if the value is in between -1 to 1
Following my comment as answer since this iif statement seems to solve your problem:
=iif(Fields!Bill.Value-SUM(Fields!Paid.Value) < -1 OR Fields!Bill.Value-SUM(Fields!Paid.Value) > 1, Fields!Bill.Value-SUM(Fields!Paid.Value), 0)