I have different user accounts, however I do not want certain admin users to be able to edit the date and the invoice number when they create an invoice. Do you have this functionality?
Currently I have the option set up for them to create invoices only, but they are still able to edit the invoice number and the date.
Permissions are not that fine-grained. You can see the problem: someone will want User A to edit everything but a carried-over purchase order reference on a purchase invoice; someone else will want User B to be able to edit dates on receipts, but not sales invoices. To implement your request would require field-by-field-by-form-by-form permissions. That really is overkill.
By the way, I am not sure how you were using the phrase “admin users,” but administrators have full access in Manager. Restricted users are the ones with limited access.