Unfortunately, the info document describing tar is licensed under the GFDL with
invariant cover texts, which violates the Debian Free Software Guidelines.  As
a result, the info documentation for tar has been completely removed from the
Debian package.  Fortunately, since 1.28 the upstream tar package includes
man page sources, so at least that documentation is included in the Debian
main tar package.

If you want to read the complete info documentation for GNU tar, please either
install the 'tar-doc' package from Debian's non-free repository, or refer to
the online version at <http://www.gnu.org/software/tar/manual/index.html>.