The 63-year-old 'Good Will Hunting' actor, who died earlier this month, was approached by bosses at AEG Live in July, 2012 to perform two headline shows at The Colosseum at Caesars Palace, reported TMZ online.
According to the document, Williams was offered USD 600,000 for the performances.
However, the funnyman turned down the proposal, and his representatives say he was committed to his TV comedy 'The Crazy Ones' at the time.
The show was cancelled after one series earlier this year.