How group works in Radius

Hi All, We are using Freeradius3. So basic authentication,authorization, accounting is working. We created group in radgroupcheck. On Register user we are storing username with group in radusergroup. So still we are not getting groupname in radacct table. So in debug we found radius only not sending groupname when it is giving input to radacct. We need group for users . Can anyone explain me on how it works for group? Thanks in advance.