The greatest harm from highway robbers lies not in seized wallets but in inhibited travel. Similarly, incentives for tax-reducing strategies put much sand in the wheels of the economy. Demands to replace our monumental tax code with a simple, graceful one that does not distort economic incentives heat up periodically in political debate, but such dreams never materialize. A FUNDAMENTAL obstacle, not yet well understood in the economic literature, is the impossibility of objectively evaluating the tax base -- assets, income, etc. One can see this even in toy examples, say, trying to assess the value of a position in chess: great masters' assessments will all differ. Here computer theory can add an insight not provided by classical economics tools. A way around is to avoid evaluations by expressing the tax in natural units, not in cash. For publicly traded corporations, these could be corporate shares. I discuss a simple (postcard-sized in ALL details) corporate tax system that avoids ANY distortion of incentives. (Tax tools MEANT to influence corporate policies should be set as explicit separate taxes or credits, open to public scrutiny, not hidden between lines of an incomprehensible tax code.) Roughly, the~system is to periodically take a t*i fraction of shares to auction, where t is the tax rate, i is the interest rate. It replaces all income taxes on publicly traded corporations, their subsidiaries, and shareholders. The interest rate is defined via specially designed bonds, so that the whole system can be shown PRECISELY equivalent to a flat tax on INVESTMENT RETURN. Note that taxing the return DIRECTLY is impossible: it would invite manipulation of stock market~prices. The main feature is that nothing corporations and investors do can change their tax (t*i fraction of shares), so they would do business exactly the SAME WAY they would WITHOUT TAXES.