This tax season may be the last in which many Americans itemize their tax returns and get a break for charitable donations.

The new Tax Cuts and Jobs Act, which applies to tax year 2018 and beyond, nearly doubles the standard deduction, which will make itemizing deductions less beneficial for many.

Indeed, the number of households to get a tax benefit from charitable contributions next tax season is expected to drop to about 16 million from 37 million, according to the Urban-Brookings Tax Policy Center, a nonprofit think tank based in Washington, D.C. 

But for your 2017 return, you can still itemize as you've done in the past. And to get the biggest tax savings, make sure you value your charitable donations correctly. Here's what to keep in mind.  

• Donate to an IRS-qualified charity. The organization you donated to must be an IRS-qualified charitable organization in order for your gift to count toward a tax deduction. If you're not sure about the charity, look it up using the IRS's Exempt Organizations Select Check.

• Don't overestimate the value of your donations. When coming up with a value, consider the item's age and quality. The IRS says that the fair-market value of used clothing and household goods is the price that buyers would pay for them in a consignment or thrift shop. Keep in mind that for a tax deduction, the IRS allows taxpayers to report only donated items that were of good quality or higher when they were donated.

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• Use valuation tools. Some charities provide valuation guides on their websites to help you figure out how big a tax deduction you should claim. You can also use tax software to value donated goods. When we judged the donation-valuation tools provided by the top three online tax-prep software brands—H&R Block, TaxAct, and TurboTax—we found that TaxAct gave the most generous valuations for 10 out of 18 randomly selected items. But only TurboTax’s donation feature, ItsDeductible, is available free to anyone online; it came in second in our test, valuing six items highest. (It's also free as an app on iOS.)

• Keep your receipts. The charity may have itemized the donations, or you may have made a list of what you gave. In either case, keep the receipts with your tax records in case you're audited.

Different rules apply depending on the value of your gifts. If you claim a tax deduction for a noncash contribution worth less than $250, the written acknowledgment from the charity should include its name, the date and location of your donation, and a description of the item or items given.

If the value of your donation falls between $250 and $500, the acknowledgment must also say whether you received goods or services in return (and if you did, an estimate of the value). For example, if you paid to go to a fundraising dinner, a portion of that might be the value of the dinner.

• Consider various options to value a car sold into salvage. If you donated a car that ended up in salvage, you'll typically get a receipt from the charity that says the car's value was worth $500 or less but doesn't get more specific than that. If you want a precise valuation, there are a number of ways that you can estimate the car's value and report that on your tax return.

Larger Donations

The more generous you are, the more paperwork you’ll have to fill out. If your gift is worth more than $500, you must fill out and attach IRS Form 8283, Noncash Charitable Contributions to your tax return. For donations valued at more than $5,000, you must have on hand an appraisal of your gift. (Only in special instances—say, you donated art valued at $20,000 or more—do you need to submit a signed appraisal to the IRS with your return.) You can deduct the cost of the appraisal if the total of all your miscellaneous itemized deductions exceeds 2 percent of your adjusted gross income.

For more information about donations of all kinds, check out IRS Publication 526, Charitable Contributions