[dboreham]

Quick note since it wasn't totally clear from the sibling comments that this is totally wrong. The cited document is describing a completely different kind of "deduction" for a completely different reason and has nothing at all to do with the ability to "deduct" business costs from profits. The underlying principle is that only profits from business activity are taxable, not gross income.

In case anyone is wondering, the cited document discusses _unreimbursed_ _employee_ expenses. This means something like: you used your guest room as an office to perform remote work for your employer, and they didn't give you any rent for that space. In some times past you could actually pay less tax by declaring that you had rented your guest room to your employer but they hadn't paid you the rent, and so that's now a loss to you upon which you don't pay tax. This document says "nope, you can't do that any more".