We have multiple clients want to add a custom field on the sales report, e.g. each sales needs to split tip income with kitchen staff, so they need add a custom field "Kitchen Tips" to the report.

The formula for this field is (net food sales + net unclassified sales) * 5%, "food" is a revenue class the merchant defined. They used to use the Squirrel POS system, which allowed them to add such a field.