Missouri Withholding calculations have been updated for 2018.
The agency increased the standard deduction and does not use any allowances in the calculation of taxes.
If there are any allowances marked on a current MO-W-4 or future updated MO-W-4 they will not be processed as the new updated calculation does not have this as part of the formula.
Pages 16-17 of the guide show the new formula if referenced.
If employee's question their tax withheld the new calculation should be considered as a reason for the change .