BRIEFLY : A tax dispute resurfaced from AT&T;’s breakup.

The Internal Revenue Service is sending letters to owners of stock in American Telephone & Telegraph Corp. reminding them that the agency has had a longstanding dispute with AT&T; over the taxability of the Jan. 1, 1984, breakup--and ordering the shareholders to see things the IRS’s way. At issue is AT&T;’s 1982 acquisition of the small bit of stock in Pacific Telephone Co. (now Pacific Telesis Group) it did not then own. The IRS calls that a taxable transaction carried through to the breakup; as a result, it says, 7% of the value of PacTel stock given to AT&T; owners on Jan. 1, 1984, should be considered a taxable dividend. The amount comes to less than 39 cents per Pacific Telesis share.