A new tax regime is on its way. Here’s how Californians can adjust. | McClatchy Washington Bureau

In just twelve days, Californians — and the country — are likely to confront a dramatically different tax code. Congress is poised to pass the first major tax overhaul in more than 30 years, sending it to the president’s desk for his signature this week.

While Republicans’ plan creates some significant loopholes for wealthy individuals, it doesn’t give the average taxpayer many ways to try and finagle the new system.

Of particular note for California, the final version of the legislation prohibits people from prepaying their 2018 state and local income taxes before the end of the year. Tax advisers had floated that idea in recent weeks as a way for individuals to save money before new $10,000 caps on state and local tax deductions kick in next year. Lawmakers mooted the option.

The Republican bill is silent, however, on prepaying 2018 state and local property taxes. That suggests Californians could pay the next installment, due in 2018, this year, and thereby increase the property tax deduction they can take on their 2017 federal returns while it’s still unlimited.

Assuming your property tax is over $10,000, such a move could save you money in 2018, says certified public accountant Wenli Wang. And “that isn’t a very large assumption given housing prices in California,” adds Wang, who is the partner in charge of accounting firm Moss Adams’ San Francisco and Walnut Creek offices.

The state and local tax deduction is one of the most popular of the itemized deductions individuals can subtract from their federal tax bill. In 2015, more than 6 million people in the Golden State claimed state and local tax deductions, worth more than $100 billion. But many of those taxpayers are likely to choose to take the standard deduction going forward, since it will be worth about twice as much in the new tax code.

For those who fall into that category, it might make sense to write some larger-than-normal checks to charity in the final days of 2017. Once you switch from itemized deductions to the standard deduction, those charitable contributions can no longer be subtracted from your tax bill.

But for those who continue to itemize their deductions in 2018, the new tax law still allows you to subtract charitable contributions.

Under the new tax plan, the cap on the mortgage interest deduction will fall from $1 million to $750,000 for new home purchases, beginning in 2018. But if you're in the midst of buying a home there's no reason to hurry and sign the mortgage in the final days of 2017 — you’re already too late to apply that higher $1 million cap. Congress added language in the final bill setting a deadline of Dec. 15 to qualify for the existing mortgage interest deduction, said University of California at Davis Law Professor Darien Shanske.

If you've already signed your mortgage contract, you have until April 2018 to finalize it and still deduct up to $1 million in interest from your 2017 tax returns.

Tax experts caution that for most people, it’s not worth altering major financial and personal decisions to try and save a few thousand dollars before the new tax regime goes into effect. For example, Shanske says your tax bill could change based on new formulas that take into account how many children you have, but “that’s not something you’re likely to manipulate.”

The bigger opportunities, tax experts say, lie in the new ways the tax code will treat corporations.

“For a long time, the top corporate income tax rate was about the same as the top personal income tax rate,” explains Shanske. The legislation moving through Congress drops the corporate rate to 21 percent, while the highest marginal tax rate is pegged at 37 percent.

For people who earn money through investments or business ownership, rather than a salary, that difference create a huge financial incentive to report those earnings as corporate —rather than personal — income, he says.

Both Shanske and Wang emphasize it will be necessary to consult a financial adviser or tax planner to figure out what arrangements makes the most sense for every individual taxpayer.

Wang says her basic advice to all her clients is: “Don’t change your life for taxes.” However, if it’s “feasible to do and makes business sense or makes sense for your personal life, why not?”

This story was updated at 10 a.m. on Wednesday, Dec. 20 to reflect that the final tax legislation will apply the lower $750,000 cap on mortgage interest deductions for mortgages signed after Dec. 15, rather than beginning Jan. 1.