Tournament referee Brian Earley issued his ruling a day after Williams was cited by chair umpire Eva Asderaki for a code violation for verbal abuse during a 6-2, 6-3 loss to Sam Stosur in the women's singles championship match at Flushing Meadows.
A statement issued by the U.S. Tennis Association said the fine "is consistent with similar offences at Grand Slam events."
Williams earned $1.4 million at the U.S. Open: $900,000 for finishing as the runner-up, plus a $500,000 bonus for having come in first place in the U.S. Open Series standings, which take into account results at hard-court tuneup tournaments.
The USTA also said Grand Slam committee director Bill Babcock conducted his own review and determined "Williams' conduct, while verbally abusive, does not rise to the level of a major offence under the Grand Slam Code of Conduct."
That means Williams does not face further disciplinary action — which could have included a fine and suspension from a Grand Slam tournament — under the "probationary period" she was put under after yelling at and threatening a line judge after a foot-fault call at the end of her loss to Kim Clijsters in the 2009 U.S. Open semifinals.
On Sunday night against Stosur, Williams faced a break point while serving in the first game of the second set.
Williams ripped a forehand that she celebrated with her familiar yell of "Come on!" But Asderaki ruled that the scream came while Stosur was reaching for a backhand, so the point wasn't finished. Based on the hindrance rule, Asderaki awarded the point to Stosur, putting the Australian ahead 1-0 in that set.
That set Williams off on a series of insults directed at the official, a scene far less ugly than — yet reminiscent of — her tirade on the same court two years ago.
A sampling of what Williams said, prompting Asderaki to call the code violation:
— "You're out of control."
— "You're a hater, and you're just unattractive inside."
— "Really, don't even look at me."
Asked at her news conference Sunday night whether she regretted any of her words, the 13-time Grand Slam champion rolled her eyes and replied: "I don't even remember what I said. It was just so intense out there. ... I guess I'll see it on YouTube."
In 2009, Williams' profanity-laced outburst at a line judge led to an immediate $10,000 fine from the U.S. Open and later a record $82,500 fine from Babcock. At the time, Babcock said that if Williams committed a "major offence" at a Grand Slam tournament in 2010 or 2011, her fine could be doubled and she would be barred from the following U.S. Open.