Can I add custom fields to the customer portal

Yes, through ticket fields. The permission decides who sees a field and whether it appears on the request form at all.

Yes, through ticket fields. The permission you set on a field decides two things at once: who can see it, and whether it appears on the request form at all. The second is where this usually goes wrong.

How do I decide who sees which field?

So a read-only field cannot be a form field. Set Customers can view expecting something the customer reads while filling in a request and it will not be there. That permission is for showing something back afterwards, such as an order reference on their request that they can see but not alter.

What to put on the form

Only what you will use. Every field is a question somebody with a problem has to answer before they can reach you, and if nobody reads the answer, or it can be looked up from what they already gave, take it off.

Fields have an internal name and a label customers see, so write the label in their words: "Which product is this about" for them, whatever your team calls it for you.

And rather than one form asking everything, separate forms per kind of request keep each one short. That is usually the better answer to a form that has grown.

See also

• Designing a form that helps agents and customers both
• What a ticket form is
• The customer portal: where customers track their requests