When are classes to similar

I would like to make report from sales data in a POS system.

So, I have a ReportGenerator that has a List <Ticket> The Ticket class represents a registration in the cash register. This can be a SalesTicket (DirectSalesTicket, InvoiceSalesTicket,...) or CashRegisterMovementTicket for a registration of money leaving or entering the cash register without a sale (e.g. taking money to the bank).

InvoiceSalesTicket has a invoiceNumber which a DirectSalesTicketdoesn't have. So I'm OK with having 2 different classes.

For CashRegisterMovementTicket I could make 2 classes (CashInRegisterMovementTicket and CashOutRegisterMovementTicket) that inherent from CashRegisterMovementTicket(which is a Ticket) that represent money that was added to the cash register or money that was taken out of the register. That would make 3 classes, that do not really differ from one another internally.

When I want to generate a report with al the money that has been taken out of the cash register I can just take the List <Ticket> and only use the ones that are of the CashOutRegisterMovementTicket type.

Another example:

SalesTicket has List <SalesLine>

Some reports are based on SalesTicket that have a gift certificate So I have NormalSalesLine and GiftCertificateSalesLine, both inherent from SalesLine but internally they are the same.

It feels like I have a lot of classes that are sometimes very similar. What am I missing?