If giving to charity is still on your agenda for 2018, there's still a window of time for you to make that year-end donation.

However, if you make a mistake, your gift might not count for the 2018 tax year.

Of note, new tax rules have made it more difficult to get a deduction for your donations. That is because the standard deduction is so much higher — about $12,000 for individuals and $24,000 for married couples who file jointly.

And your donations (plus any other deductions such as mortgage interest, etc.) must push you over the standard deduction in order for you to itemize on your tax return.

A congressional report earlier this year estimated that just 18 million households would itemize this year, down from 46.5 million in 2017.

If you're one of them, you need to get started now.

"We're running out of time, so you need to do it earlier rather than later," said Michael Duffy, director of the Strategic Wealth Advisory Group at Merrill Lynch Private Banking and Investment Group.

There are rules you need to pay attention to, such as whether you're giving to charity or to friends and family, and how you're giving, such as cash, securities or tangible property.