Google said that if you don’t need an XML sitemap file anymore, all you need to do is delete the sitemap file from your server and CMS. There is not much more you need to do after that, just delete it.
Here is John Mueller of Google’s tweet on this:
If you don’t need the sitemap file anymore, you can just delete it.
— 🍌 John 🍌 (@JohnMu) June 7, 2021
Just keep in mind, Google also said that having an XML Sitemap file is “a minimal baseline for any serious website.” So it is something you probably should have for most substantial websites.
But if you have a small website (10 pages or so), you really do not need a sitemap file.
Forum discussion at Twitter.