Gerard N. Magliocca (Indiana-Indianapolis), Escrow of Capital Gains Taxes on Stocks and Bonds:

Here’s a question for tax experts out there.  Why don’t brokerages
escrow capital gains taxes in a manner similar to a bank escrow of
property taxes on a mortgage?  It would seem to make sense from the
perspective of the customer (you wouldn’t have to pay capital gains as a
lump sum every quarter or every year), and from the perspective of the
IRS (they could more efficiently collect taxes from a small group of
brokerage firms and could, in theory, collect them in real time)?  Is
there any reason why this practice is not used?