Not only do html and body auto-close, their tags including start-element tags can be omitted alltogether:

    <title>Shortest valid doc</title>
    <p>Body text following here

(cf explainer slides at [1] for the exact tag inferences SGML/HTML does to arrive at the fully tagged doc)

[1]: https://sgmljs.sgml.net/docs/html5-dtd-slides-wrapper.html (linked from https://sgmljs.sgml.net/blog/blog1701.html)