The Virginia Supreme Court held that the Arlington County Commissioner must defer to the Virginia Tax Commissioner regarding the methodology for calculating a local Business, Professional, and Occupational Licenses tax (“BPOL”) deduction. Arlington County levies a BPOL tax based on the gross receipts attributed to activities conducted at an Arlington definite place of business. Virginia allows a deduction for any gross receipts attributable to business conducted in another state or foreign country where the taxpayer is liable for a tax based on income. Virginia law does not prescribe a methodology to calculate the deduction. The Arlington County Commissioner determined that the deduction must be established by manual accounting. On appeal, the Virginia Tax Commissioner determined that the Arlington County Commissioner used an incorrect methodology; if manual accounting is impossible to calculate the deduction, the taxpayer must use payroll apportionment. The lower court rejected the Virginia Tax Commissioner’s methodology as “erroneous, contrary to law and precedent, and arbitrary and capricious in its application.” The Virginia Supreme Court reversed, holding that because Virginia law leaves unresolved the permissible methodology for calculating the deduction, “the plain and unambiguous statutory language allows for the administrative agency whose duty it is to administer and enforce the tax laws—that is, the Department of Taxation and the Tax Commissioner—to decide how such a deduction may be calculated.” Nielsen Co. (US) v. Cnty. Bd. of Arlington Cnty., 767 S.E.2d 1 (Va. Jan. 8, 2015).