"It's been lodged and that's the only thing I can say to you," Hewitt's manager Rob Aivatoglou told Reuters.
Lawyers for the 22-year-old Adelaide resident lodged papers in the South Australian Supreme Court, a report on the Australian Broadcasting Corp. Radio website said.
The governing body for men's tennis said in April they were not intimidated by Hewitt's threat of legal action if the $20,000
The ATP originally fined Hewitt half of the prize-money he earned at the Cincinnati event -- some $105,650.
The world number two appealed and, after a two-day hearing in February, a three-member appeals committee confirmed the violation but reduced the amount to $20,000.