Although some 360,000 state income tax rebate checks already have been processed, some taxpayers still haven't gotten back their share of the state's $110 million surplus.

There are enough of them that the line to the state Division of Finance office handling their calls is often busy - so busy that callers may have to listen to a recorded message asking them to be patient.Burke Tangren, the division's chief of accounts receivable, assures taxpayers that all who paid their 1987 state income taxes by Oct. 15, 1988, will receive a rebate.

The question, though, is when. State officials are hoping to have all rebates in the hands of taxpayers by mid-November, in plenty of time for Christmas shopping.

Taxpayers who filed their returns on time without errors should have received their rebate check by now, as the last of those checks were mailed out on Oct. 11.

However, hundreds of those 360,000 checks mailed out over the past month already have been returned to the state because the taxpayers' addresses have changed and they could not be delivered.

Taxpayers who have moved since filing their 1988 returns should notify the state Tax Commission of their new addresses. If they haven't, their rebate checks already may have been passed along to the state Division of Finance.

The division is sorting through the checks returned and should be able to tell taxpayers whether their rebate checks have been returned after Saturday.

Those rebate checks that are returned to the state will be held for one year by the division. After that, they are turned over to the state treasurer's office.

Although address changes have created the biggest headache for the state, other problems have delayed rebate checks. Some have been delivered to taxpayers, but then lost.

In that case, Tangren said, a new check can be issued after 60 days of the date of the original check. He said the most interesting call received so far by the division concerned a missing rebate check. It came from a woman who claimed her check had fallen out of the mailbox and was eaten by snails.

Other taxpayers are likely to be surprised to learn that the state has withheld their rebate checks to pay for back child support or college tuition payments through the same program that allows regular tax refunds to be used towards such debts.

And taxpayers whose rebates amounted to less than $10 won't get a check at all. Instead, that amount will appear on their 1989 income tax form as a credit towards taxes owed.

The rebates were proposed by Gov. Norm Bangerter as a way to return $80 million of the state's $110 million surplus to taxpayers. The rest of the money was split by the Legislature between education and the state's so-called rainy-day fund.

Taxpayers who suspect an address change may be holding up their rebate check should contact the state Tax Commission at 530-6562. For other help in tracking down a check, contact the state Division of Finance at 538-3202.