# EPUBCheck OPF-048: Package tag is missing its required…

Source: https://epublab.com/epubcheck/opf-048/ (updated 2026-11-03)

EPUBCheck OPF-048 is an error message: “Package tag is missing its required unique-identifier attribute and value.” The package element has no unique-identifier attribute, which is required.

- Official message (EPUBCheck 5.4.0): Package tag is missing its required unique-identifier attribute and value.
- Default severity: Error

## Typical causes

- A package document written by hand or by a tool that omitted it.

## How to fix it

- Add unique-identifier with the id of the book's main dc:identifier, for example <package version="3.0" unique-identifier="uid">.

Message text and severity: EPUBCheck (W3C, BSD-3-Clause). Explanation: EPUBLab.