Mail carriers may not be smiling Tuesday, but other Utahns are likely to welcome the first batch of 40,000 income tax rebate checks.The average amount of each rebate check is $148, according to the Utah State Tax Commission. Some 444,000 taxpayers can expect to receive their money by the end of the month.

The checks are not being sent out in any particular order, according to State Accountant Pierre Carlson, so taxpayers shouldn't be alarmed if their neighbors get their checks first.

The Tax Commission will be sending out similar-sized batches of checks every Monday, Tuesday and Wednesday through Sept. 26. The first batch is being sent on a Tuesday because of the Labor Day holiday.

The amount of the tax rebate is 12.5 percent of the total state income taxes paid in Utah in 1987. Those who paid less than $80 in taxes last year will be able to deduct the rebate amount from their 1988 income taxes, since the total would be less than $10.

The rebate program was proposed by Gov. Norm Bangerter and approved in a special session of the Legislature as a way to use some $80 million of the state's $110 million surplus.

Public schools were given $10 million of the surplus, which resulted from tax revenues coming in at a higher rate than projected, and the rest was set aside in a "rainy day" fund.

Plenty of people, including Uncle Sam, already have their eye on the rebate checks. The Tax Commission reminds tax payers that the rebate may be subject to federal taxes.

However, taxpayers can donate their rebate money to charity, making it tax-deductible. The checks carry the message that the rebate dollars given back to specific state programs are also tax-deductible.

Telephone numbers for a variety of state programs, including education, health and social services are listed on the checks, which cost the state $286,000 to process and mail.

And the Tax Limitation Coalition, which successfully petitioned to get the three tax initiatives on the November ballot, has suggested that it too is a worthy recipient of tax rebate dollars, since it's fighting for lower taxes.

Taxpayers who have yet to pay their 1987 state income taxes must do so before Oct. 17 to qualify for a rebate.

Tax Commission figures show that some 52,000 Utahns still owe about $26.5 million in back taxes.

Money owed for unpaid student loans, delinquent child support payments or similar debts will be deducted from the rebates through the Tax Commission's GOTCHA program.