When you see E&OE on a bill, it means that mistakes and omissions are okay. It’s a type of disclaimer for clerical errors that can happen on invoices, but there doesn’t have to be an error for someone to use it.
Sometimes, a vendor or business owner makes a mistake on an invoice by accident. This disclaimer is meant to protect them in case they make a mistake or forget something. This helps protect the person who wrote the invoice in case they make a mistake when adding up the total amount of the invoice or with anything else on the invoice.