What tax reform means for the next big lottery winner

One thing is for sure -- the new law cut the top federal income tax rate from 39.6% to 37%. And when you're talking about hundreds of millions of dollars, those 2.6 percentage points could mean a huge windfall for a winner. 

The Powerball jackpot now stands at $460 million, with the next drawing set for Wednesday night, and the Mega Millions drawing this Friday will pay a top prize of $418 million. But those prize totals only apply to winners who take the payout over the course of 29 years, and virtually no one does that. 

Most winners take a lump sum payout, which would come to an estimated $291 million for Powerball, and $261 million for Mega Millions. And 2.6% of those jackpots comes to a savings of $7.57 million for Powerball, and $6.79 million for Mega Millions.

The bad news is that most winners will also owe a large state tax bill, and state income tax payments are no longer entirely deductible from federal taxes. Post tax reform, that deduction is now limited to a relatively modest $10,000, which will probably go a long way to offsetting the new, lower federal tax rate.