The changes in the Tax Cuts and Jobs Act signed into law late in 2017 will be reflected in 2018 tax returns, which are filed this spring. The law is one of the most sweeping tax code reforms of the last three decades, and it is likely to affect all Americans who file tax returns. Many of its provisions are certain to affect retirees. Here's a look at four of the most significant.

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1. The standard deduction is nearly doubling.

Deductions are amounts subtracted from income, lowering the taxable income and thus reducing the total amount owed in tax.

Taxpayers must choose between two categories: the standard deduction and itemized deductions. If filers choose the standard deduction, they exclude a set amount from their income. If they choose to itemize, they subtract the dollar value of each deductible category.

The new tax law almost doubles the standard deduction, from $6,350 to $12,000 for single filers, and from $12,700 to $24,000 for married people filing jointly. 

On the face of it, the considerable hike in the standard deduction sounds significant. It may not be as far-reaching as it initially seems, though. In years past, filers using the standard deduction could include a personal exemption as well, as long as no one claimed them as a dependent . For 2017, for instance, single filers using the then standard deduction of $6,500 could also subtract $4,150 from their income for a personal exemption, making the total adjustment $10,650.

But the personal exemption was eliminated under the Tax Cuts and Jobs Act, so folks taking the standard deduction for 2018 won't have access to also taking a personal exemption any longer.

The jump in the 2018 standard deduction thus represents more of a muted increase from the former standard deduction plus personal exemption level, rather than effectively doubling the past standard deduction. The gain is more than 12% for a single filer, for instance. That's still a nice increase, and it more than makes up for the elimination of the personal exemption. But it's just not as much as an initial comparison of amounts might lead you to believe.

The increase in the standard deduction has the resulting effect of making itemization necessary for fewer people, including retirees. In the past, itemizing as many deductions as possible was the smartest move, as long as the total exceeded the amount of the standard deduction plus the personal exemption. Common deductions included mortgage interest up to $1 million, a level that the Tax Cuts and Jobs Act has now reduced to $750,000. 

The rise in the standard deduction might mean that retirees can achieve roughly the same overall deductible by taking the standard amount as they could by itemizing. Once you get an idea of what your itemized deductibles add up to, you can decide whether itemizing still makes sense. If not, taking the standard deduction can save time, effort, and tax-preparation expenses.

2. The deduction for state and local taxes has been capped.

There's also a brand new cap on another widely used deduction: state and local taxes, including property tax (SALT). In the past, the total could be deducted, period. Your SALT total made no difference to its deductible status. But for 2018 and beyond, SALT deductions are restricted to a total of $10,000.

For retired filers whose SALT is less than $10,000, there is essentially no change stemming from the SALT cap, although they should consider the advisability of choosing itemization or the standard deduction.

But for many retirees, especially in high-tax states like California, New York, and New Jersey, the SALT cap could have significant repercussions, for three reasons.

First, if your SALT total is considerably more than $10,000, you are losing one of the financial incentives to own a house. You will no longer be able to deduct all your SALT, which may make owning a property less appealing.

Second, the SALT cap may make downsizing more desirable for homeowners in high-tax jurisdictions. Property taxes, for example, usually depend upon real estate size: A 700-square-foot condo is likely to be assessed considerably less in taxes than a 15,000-square-foot house. Retirees with high property taxes may end up taking a hard look at their property footprint.

Third, it may become less appealing to live in a state with high taxes. Many states have no state income taxes, after all, including Alaska, Florida, Nevada, South Dakota, Texas, and Washington. States also vary widely in the amount of property tax and sales tax assessed. Localities vary in the respective taxes levied. In the wake of the cap, all these levels may receive increased scrutiny as a factor in real estate desirability.

Many retirees think about moving to eliminate the maintenance costs for a large property or to live near grown children (or both), but then they don't actually make the move. The SALT cap could be an impetus to make that thought a reality, especially if the state of your dreams has more-favorable taxes.

3. Taxpayers may be able to deduct more for healthcare expenses.

For the last several years, filers could itemize and deduct healthcare expenses totaling more than 10% of adjusted gross income (AGI). Under the new tax law, healthcare costs are now deductible if they exceed 7.5% of your AGI. This increased deduction potential was made retroactive to 2017 taxes as well.

AGI is calculated  by totaling all income for the year (wages, bonuses, dividends, and so forth) and subtracting allowed adjustments, such as qualified retirement account contributions and alimony. AGI, which can be found on the Internal Revenue Service's 1040 form, is the amount from which deductions, whether they're standard or itemized, are subtracted. Because many deductions depend on percentages or totals of the AGI, the amount is a significant one for tax purposes.

If your AGI was $65,000 in 2016, for example, you would have needed healthcare expenses of more than 10%, or $6,500, to utilize the healthcare deduction. If your AGI was $65,000 in 2018, though, you can itemize the deduction if they exceed 7.5%, or $4,875.

The increased potential to deduct is likely to affect retirees, who have high healthcare expenses. A couple needs an estimated $399,000 saved by age 65 to meet healthcare costs in retirement, according to the nonprofit Employee Benefit Research Institute, roughly $19,950 out of pocket per year over 20 years.

Note that health savings accounts (HSAs) can make any healthcare cost bite more palatable, by providing participants with a tax deduction in the year of contribution and tax-free withdrawals. HSA maximum contributions for 2018 are $3,450 for an individual (up $50 over the prior year) and $6,850 for a family (up $100). (For 2019, the maximum climbed again, to $3,500 for individuals and $7,000 for a family.) Contributors who are 55 or older are still allowed a $1,000 additional catch-up contribution.

4. Tax rates lowered in most brackets.

Tax rates were lowered almost across the board under the new tax law. As a result, many retirees will pay less in taxes.

While there are seven tax brackets for 2018, just as there were in 2017, the rates and income associated with most brackets have changed. Although the lowest tax bracket remains the same -- 10% for those who make up to $19,050 -- taxes for most others are falling.

Single filers who made between $19,050 and $77,400 during 2017 were in the 15% tax bracket for example. For 2018, people with incomes in the same range are in the 12% tax bracket. Single filers who made between $77,400 and $156,150 in 2017 were in the 25% tax bracket. For 2018, they will pay 22% in tax on income in the same range. Look here for a full comparison of brackets, respective income ranges, and percentage changes under the new tax law.

It's likely that some aspect of the new tax law affects you -- maybe even to a great extent if you're a retiree. Reviewing these four categories will help you plan your tax return for maximum benefit.

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