  In this article we show that the payment flow of a linear tax on trading
gains from a security with a semimartingale price process can be constructed
for all c\`agl\`ad and adapted trading strategies. It is characterized as the
unique continuous extension of the tax payments for elementary strategies
w.r.t. the convergence "uniformly in probability". In this framework we prove
that under quite mild assumptions dividend payoffs have almost surely a
negative effect on investor's after-tax wealth if the riskless interest rate is
always positive.
