If you have several Google accounts, please make sure to log into the correct account in advance, because it is also possible as an individual to submit several reviews with the corresponding user account.

You can easily see whether and in which account you are currently logged in on the Google homepage in the top right corner, and there you can also switch back and forth between your accounts.

See fig. (Click to enlarge)

After you have logged into your Google account, go to the official Google Maps page at https://www.google.com/maps/ and click on “My Posts” in the menu. There you will also find the sub-item “Reviews”, under which you can view, edit and delete your previous reviews.

Please keep in mind that it may take some time before your updated rating is publicly available, as this process is also checked again.

See fig. (Click to enlarge)

So it is actually pretty easy to change or delete a rating once it has been submitted. Because on the one hand, opinions sometimes simply change after you have had very positive experiences with the company later, or the other way around, everything is much worse and you want to express your displeasure.

Note:
However, always make sure to remain factual in your reviews. Please do not start with personal mention of names, or worse, utter insults.

So if you write for example:

Mr / Ms XYZ is the greatest id … t ever walking around. How can such a sh…t company survive ??? !!!,

then this is not only irrelevant, but can also cause legal problems due to your insults. In case of doubt, such reviews are rightly not published by Google. Because the possibility of submitting reviews does not serve to get rid of your frustration, but rather to help the whole community with your experience in the decision-making process.