Is it okay if the portfolio doesn't have a back cover?

Because the back cover of the portfolio is not important and necessary, but it is better to have a back cover.

The back cover, also called the fourth cover and the back cover, refers to the bottom of the book cover, which is an important part of the book and an extension, supplement, generalization or emphasis of the cover and spine. The back cover and the cover are closely related, complementary and indispensable.