Each report will have different information so I would need to use a different layout for each employee.
That's not really the case. You can use the same layout but pull up different records for each employee. You'll only need a different layout if the format or the type of information reported is different.
You'll have to describe what you mean by "5 entries" and "4 entries". Is this data entered into a single field, multiple fields, records in a related table?
A table of related records linked to both invoices and employees is probably what you need here in order to get your report.