This is what I found, from Virginia Dept of Revenue:

• Fiduciary Income Tax: Beginning with returns due on or after January 1, 2020, tax preparers are required to file fiduciary income tax returns electronically, but there is no requirement to make payments electronically.
• Individual Income Tax: Paid tax preparers who prepare, or employ people to prepare, 50 or more individual income tax returns a year are required to file electronically. If they prepare 50 or more returns in a taxable year, then for each year after, they must file all individual income tax returns electronically