Hi,
the account is different in an AB than in an "enskild firma" so you need to add more information to your question, including which type of tax you are posting.
In the AB, the tax account is acct 1630. When the AB pays the preliminary income tax F-skatt, it is posted to acct 2518 Paid corporate tax and credited acct 1630. In the EF, the F-skatt is posted to 2012 or 2013 as it is not a tax payable by the EF but the person running the EF.