Half of survey respondentsdidn't know how much tax was withheld from their paychecks andtherefore probably wouldn't be able to say how much they pay intaxes each year. (Photo: Bloomberg)

Taxation may be one of only two certainties in life, but manyAmericans know very little about how it affects them.

In a recent survey of 1,000 U.S. adults conducted byBetterment, an online financial broker, 85 percent of Americanssaid they felt at least somewhat confident about their knowledge of taxes.

And yet, half of respondents said they didn't know how much taxwas withheld from their paychecks and therefore probably wouldn'tbe able to say how much they pay in taxes each year.

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Nearly as many—48 percent—weren't able to say whether their taxrates changed in the past year. Thus, they are unaware of how thetax overhaul approved by Congress at the end of 2017 affected them.Despite this, 18 percent of respondents say they increased their401(k) contributions as a result of the reform bill.

Finally, 23 percent didn't know that the filing deadline wasApril 15. One can only hope they believed the deadline was earlierand haven't been paying late fees.

Millennials and Generation Z (those born after 1997) were themost likely to express confidence in their knowledge of the taxcode. But that same group was also much more likely than theirelders to not know when the filing deadline was.

There are some who do seem to get it when it comes to incometaxes. Forty percent of respondents say they sold stocks for a taxbenefit, and an third made charitable donations.

Roughly a quarter of respondents said that they had beennegatively impacted by the government shutdown earlier this year, withone-third saying they had to tap emergency funds as a result.

While 28 percent said they planned to file taxes earlier thanusual because of the shutdown, 10 percent said they planned to filelater. Most of those paying earlier said they felt additionalpressure to file because they worried the government would takelonger than usual to get them their refund, while late-payerslargely said they felt less pressure to pay on time because theyfigured there would be less accountability due to the turmoilcaused by the shutdown.

Read more: 

• Republicans weaving retirement & savingsprovisions into Tax Reform 2.0
• Tax refunds mean doctor visits for manyAmericans
• Tax refunds can pay off for retirementsavings