William J. Quirk in The American Scholar:
Several years ago, my colleague and friend Matthew Bruccoli, an English professor and author of books about 20th-century American writers, made a surprising request. He said he had F. Scott Fitzgerald’s income tax returns covering his working life, 1919–1940, and asked if I would like to write an article with him based on the returns. Matt was for many years a good friend of Fitzgerald’s daughter, Scottie, and in her will she had appointed him a trustee for the trust she had set up for her four children. It seemed to me such an amazing find; I asked Matt how he had obtained the returns. One day, he said, while he was helping Scottie organize things, they came across the tax returns. Scottie, saying that they wouldn’t interest anyone, was going to throw them out. Matt, who didn’t believe in throwing anything out, asked if he could take them. He sent the returns to me; Matt’s death in June of 2008 meant I would have to write the article without him.
What can be learned from Fitzgerald’s tax returns? To start with, his popular reputation as a careless spendthrift is untrue. Fitzgerald was always trying to follow conservative financial principles. Until 1937 he kept a ledger—as if he were a grocer—a meticulous record of his earnings from each short story, play, and novel he sold. The 1929 ledger recorded items as small as royalties of $5.10 from the American edition of The Great Gatsby and $0.34 from the English edition. No one could call Fitzgerald frugal, but he was always trying to save money—at least until his wife Zelda’s illness, starting in 1929, put any idea of saving out of the question. The ordinary person saves to protect against some distant rainy day. Fitzgerald had no interest in that. To him saving meant freedom to work on his novels without interruptions caused by the economic necessity of writing short stories. The short stories were his main source of revenue.
More here.