I don't pretend to have all answers about age limits on taxes in VA, but while looking at films showing personal tax in Berkeley Co. VA (now WVA) from 1782-99, I found a note attached on the film for the county. All males were required to be in a county militia from age 16-50 per the Act of May, 1777. Tax lists were developed from these militia lists. Thus, the tax lists were split into military districts or battalions. In the 1790s, districts started developing with names attached to the list taker. These lists generally followed a standard form - white males 16 and up, blacks (slaves) 21 up, blacks 16-21, horses, sometimes cattle, town lots, billiard tables, stud horses. This form generally stayed the same into the 1800s, but the white poll age could change its limits. The same form spread to NC, TN, and other southern states - with variations of course. One funny thing from our point of view - one TN county started taxing dogs - it is was the first column on the ! list. The second column was designated for bitches. Almost every man had his hunting dog, and it was unusual if more than one dog was listed. Sometimes I wonder how a tax collector counted all of the puppies - or at what age they started to count. I can also see that when a tax collector appeared in the neighborhood, the men took their dogs into the hills for a time so they wouldn't be counted. Times have changed, but yet, they haven't.