The largest tax refund windfall in Oregon history will start showing up in mailboxes over the next two weeks.

Kicker checks are in the final stages of printing in Salem, and a Department of Revenue spokesperson said they must be in the mail by December 15.

"We have been printing since last month and we are in the home stretch right now," said Rosemary Hardin.

This year's kicker pool is $1.1 billion, split over 1.7 million Oregon taxpayers. By law, when state revenues exceed 2% of projections over a two year period, the rest is refunded to taxpayers. It's the only law of its kind in the nation.

Hardin says most taxpayers will receive at least $200.

"The median is the number we like to use, and that's $297," she said. "Half will be more than that, half will be less." Hardin says the average kicker check will be around $600.

To calculate your kicker amount, take the figure from your 2006 Oregon return, Form 40, line 29; Form 40S, line 13; Form 40N, line 51; or Form 40P, line 50, then multiply that number by 18.6%.

The state's choice to mail out kicker checks instead of giving taxpayers a credit on their next state tax return is expensive. It costs $1.3 million to produce, process, and mail the checks.

Calculate your refund

The process was totally automated, right down to the envelopes. The Oregon Office of Publishing and Distribution prints out the checks and completes the mailing process.

 Video: Kicker checks - hot off the presses

(KGW reporter Dave Northfield also contributed to this article.)