Any changes that retroactively apply to 2018 VA taxes will likely take a few weeks to get implemented in the software.
..there are no light-switch changes possible.
IF.. any changes retroactively applied to 2018, the state DOR will first have to tell the software companies how they want them implemented...that alone would take a week or two...then another couple weeks for the software companies to implement and get the changes approved thru the VA DOR before rolling them out.
https://tax.virginia.gov/sites/default/files/inline-files/tb-19-1-date-irc-conformity-advanced.pdf
____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*