To enter the Basic Military Pay subtraction in TaxACT:

1. From within your TaxACT return (Online or Desktop) click on the State Q&A tab, then click Virginia directly below the blue tabs
2. Click Adjustments to expand the category and then click Adjustments subtracted from income
3. Click Other Subtractions
4. Select 38-Basic Military Pay from the drop-down menu and enter the appropriate amount(s)

Additional information, per the Virginia website Military Tax Tips:

Military personnel stationed inside or outside Virginia may be eligible to subtract up to $15,000 of military basic pay received during the taxable year, provided they are on extended active duty for more than 90 days. For every $1.00 of income over $15,000, the maximum subtraction is reduced by $1.00. For example, if your basic pay is $16,000, you are entitled to deduct only $14,000. You are not eligible for the subtraction if your military basic pay is $30,000 or more.