To answer your question, there are a few things I think that are implied in that. You say that a lawyer paid tax in one year and then after the end of the year determined the amount to be uncollectible or a bad outcome. In the first year, they would have had to have made the determination that it would likely result in income. Again, it's the same sort of determination as an engineering firm that gets paid at the end of the project. It's the world that they're already in, but for lawyers, of course, you win or lose—it's binary—court cases sometimes.
If you made that determination, you include it in your income in year one. Then you would have a writedown in year two and you'd have a deduction or a loss in that year.