Local government elections were held on Saturday for all but one of the state's 128 councils.
While some candidates were declaring victory on Sunday, the full results won't be announced until early October.
"The count cannot be concluded until all postal votes have been returned to the Electoral Commissioner," a NSW Electoral Commission spokesman said in a statement.
Postal votes can still be returned until September 27, and about 1.5 million people, or one in four, opted to vote early.
The Labor party looks set for a sweeping victory in the Inner West council, securing more than 40 per cent of votes in all wards and leading in all but Stanmore, where the Greens have won 44.5 per cent so far.
Australia's longest-serving lord mayor, Clover Moore, all but declared victory for a record sixth term after winning almost 37 per cent of the vote, followed by Labor on 17 per cent and the Greens on 13 per cent.
Several councils could be lurching to the left after the Liberals failed to nominate 136 endorsed candidates, a debacle that could significantly reshape local government for the next four years.