https://checkstyle.org/config_javadoc.html#WriteTag

$ cat Test.java
public class Test {}

$ cat config.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE module PUBLIC
        "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
        "https://checkstyle.org/dtds/configuration_1_3.dtd">
<module name="Checker">
    <module name="TreeWalker">
        <module name="WriteTag"/>
    </module>
</module>

$ java -jar checkstyle-10.2-all.jar -c config.xml Test.java
Starting audit...
[ERROR] C:\workdir\Test.java:1: Type Javadoc comment is missing null tag. [WriteTag]
Audit done.
Checkstyle ends with 1 errors.

Expected: no violation, since there is no javadoc.
Also note confusing violation message ("null" tag).

For javadoc presence there are other checks. And docs mention that with default config it does nothing, but it reports weird message instead.

P.S. Checkstyle has WriteTag with default config -

Breaking behavior compatibility migration notes:
No configuration breaking changes. Breaking compatibility is only in behavior - so it is defect/bug fix.
after fix and release (10.21.0) Check will not report violations on missed Javadocs.
To archive behavior as before, users should start using InvalidJavadocPosition, MissingJavadocMethod , MissingJavadocPackage , MissingJavadocType to let Checkstyle demand javadoc first and when WriteTag will demand required tag in existing javadoc