Withholding calculations versus liability are at their worst (that I can remember) based on the manipulation by the current administration (to say they boosted take home pay).
Even though I do not directly deal with employees, I suggest my customers give employees notices about checking their withholding early in the year, and again at the end of Q3. From the perspective of my customer, the idea is to reduce the number of employees who blame their employer for under withholding. The IRS has provides documents employers can post/hand out, including the recent "whoops, we screwed up and will not charge interest on certain under withholding situations".
---
Yes indeedy thank you, I have lost customers this year based on this very issue. The complaint is the calculations I built in to my payroll software did not withhold enough. Of course, I use the official IRS instructions, but they still think it must be my fault their employees owe money. Self responsibility, like what used to be common sense, is no longer the norm.