States will find out how much GST revenue they will gain or lose under the new formula when a report is released in June.
Prime Minister Malcolm Turnbull says the Productivity Commission's report on the GST breakdown will be released before the Super Saturday by-elections.
"The government has committed to release the report in June," Mr Turnbull told parliament on Wednesday.
Tasmanian independent MP Andrew Wilkie asked if the new formula would make sure his state did not lose out.
Mr Turnbull said the payments Tasmania received would not be reduced by "one cent" but he did not address whether the formula would disadvantage the state.
"It is also important that any new arrangements are seen as being fair everywhere," Mr Turnbull said.
"It has to pass the pub test in Burnie, as it does in Bunbury, Ballarat and Bendigo, right around the country."
Any change to the GST could affect the coalition's chances in by-elections in Tasmania, South Australia and Queensland on July 28.
But the Liberals are not standing candidates in Western Australia, which is where the push to change the GST formula has been the strongest.
A change could result in Tasmania and South Australia losing some of their allocation, which is already above the amount of GST they raise.