Solved
Can they fine us even though we filled out our W-2 on the conservative side?
Yes, the IRS can impose civil penalties for being underpaid through withholding or estimated tax deposits.
However, even the IRS recognizes that the many tax changes that become effective in 2018 led to widespread confusion, and has provided some measure of relief to those taxpayers whose taxes were underpaid despite good faith efforts. The following article from The Journal of Accountancy explains the new IRS relief provisions:
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