New tax deduction cap could turn big refund into big tax bill

The big tax question of the year: Will you get a super-sized refund or suddenly discover that you're going to end up writing one monster check?

No one really knows for sure in light of sweeping changes that hit homeowners, two-paycheck couples and families who once had a string of itemized deductions but no longer can take some breaks under the Tax Cuts and Jobs Act of 2017.

Taxpayers are getting their first look at how the new tax overhaul hits their pocketbooks when they file their 2018 federal income tax returns. The devil involving those deductions, such as those for property taxes and state income taxes, is in the details.

If you think you're getting the same tax refund as last year – or even bigger with the tax cuts – think again. It's not that simple. Some are owing more money.

A Novi, Michigan, homeowner told me he was shocked when he was smacked with having to write a big check to pay his tax bill after he completed his 2018 tax return.

He owes more than $3,000 when typically he received roughly a $4,000 refund in the past.

The couple, in their 50s, both have jobs and receive W-2s to report their wages. They pay about $9,000 in state income taxes and another $10,000 or so for property taxes on their Novi condo. Their children are older and don't qualify for any child tax credit.

The homeowner asked to remain anonymous, citing a desire to keep his family’s financial situation private.

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The homeowner told me that he understood there was a $10,000 limit on how much one could deduct for property taxes on the federal return, after the major tax overhaul.

What he didn't know: The $10,000 cap includes much more than property taxes. The limit also impacts how much the couple can deduct when it comes to what they paid for state income taxes.

Together, what would have been more than a $19,000 deduction was limited to $10,000.

"Your total deduction for state and local income, sales and property taxes is limited to a combined, total deduction of $10,000 ($5,000 if Married Filing Separate)," according to IRS Publication 5307, which outlines basic changes in the tax package.

"Any state and local taxes you paid above this amount cannot be deducted."

Will you be able to deduct state income taxes?

Many homeowners who itemize need to dig a little deeper into what's known as the new SALT tax cap – the state and local tax deduction.