“Companies can already write off 100% of their investment in plant and equipment. It is a business expense that offsets profit.”
No, they can’t. At least not during the first year purchased. The IRS forces businesses to write off capital investment over many years, a small amount each year. One exception is Section 179 depreciation, which allows very small business to write off a very small amount of investment during the first year.
In the first year, you can expense $250,000 plus 50% of the investment. The remaining 50% is depreciated over the next few years depending on which schedule you use. My point was that capital expenses are still 100% deductible, if not wholly within the first year.