> Any sensible income tax law will allow you to offset losses against gains.

Yes, but losses, gains, revenue, and expenses are not necessarily well-defined. (Heck - even whom is incurring those things is also variable.)

And then there's the big problem - the US govt likes to encourage (and discourage) things via the tax code. GE takes advantage of that as well.

Why doesn't a revenue tax make sense? It may well take a lot more money to regulate an industry involving a great many transactions.

The main problem with a revenue tax is margins.

If you apply the same rate of taxes to all companies with the same revenue, regardless of their margins you have your choice of putting all low margin business out of business by assessing a tax higher than they can pay (to collect reasonable revenues from the high margin businesses), or leaving a lot of cash on the table in high margin industries (which as a tax authority you probably don't like).

> Why doesn't a revenue tax make sense?

Suppose there are two companies. The first company buys resource A for 100$ to produce B. The second company buys B for 110$ and produces C, which it sells to the public for 120$. A merger of both companies would approximately half their total revenue, but wouldn't change their total profit.

We don't want the tax system to determine the optimal size of a company.

Maybe it does make sense in some circumstances, I'm no economist. But it's not what we have. We have an income tax. So it doesn't make sense for people to shit on GE for this.