If some in Congress can get their way, stock investors will pay a tax on their executions.

In an article that first appeared in the New York Post, Sen. Kirsten Gillibrand now favors a new charge on Wall Street and investors that could cost billions. The Securities Transaction Tax (STT) is also backed by Sen. Bernie Sanders.

The tax, which has been proposed and defeated several times, has been called a progressive measure. Advocates say the tax is a good idea because it is relatively small and could be spread across a broad investor base, the Post noted.

Also known colloquially as the “Robin Hood tax,” this measure if passed into law would add .03 of a percent to every securities trade, she said that “the greatest risk we have to our democracy now is income inequality.”

While that’s only $3 on a $10,000 order that small investors may place directly, the big fund managers that manage our 401(k)s or pensions trade in much larger sizes than that — and those costs can add up quickly.

Gillibrand, in a prepared statement said the tax would help the economy grow. It is an idea, she added, “that has worked in other countries.”

Gillibrand contends the STT “is one example of how Congress can ensure that we reward companies that reward work, not hedge funds using high-frequency trading.”