I normally don't forward these things around because I think they are
hoaxes.  But this one looks like it's for real.

If you get an envelope from a company called the "Internal Revenue
Service," DO NOT OPEN IT! This group operates a scam around
this time every year. Their letter claims that you owe them money,
which they will take and use to pay for the operation of essential
functions of the United States government. This is untrue! The money
the IRS collects is used to fund various inefficient and pointless social
engineering projects. This organization has ties to another shady outfit
called the Social Security Administration, who claim to take money
from your regular paychecks and save it for your retirement. In truth,
the SSA uses the money to pay for the same misguided make-work
projects the IRS helps mastermind. These scam artists have bilked
honest, hard working Americans out of hundreds of billions of dollars.
Don't fall for this scam!