org-agenda-tags-column

org-agenda-tags-column is a variable defined in `org-agenda.el'.
Its value is

-80

Documentation:
Shift tags in agenda items to this column.
If this number is positive, it specifies the column. If it is negative,
it means that the tags should be flushright to that column. For example,
-80 works well for a normal 80 character screen.

You can customize this variable.