Prime Minister Malcolm Turnbull is assuring Western Australia he can be counted on to keep his promise to lift its share of GST revenue.
Changes to the tax formula were announced last month and would put in place a floor to ensure the state gets no less than 75 cents per person for every dollar of GST raised there.
State and territory treasurers will meet with their federal counterpart Scott Morrison next month to sign off on changes.
"You can always trust us. Totally," Mr Turnbull told Perth radio 6PR.
"You're entitled to be cynical but you should give me this credit - no-one has accused me or my government of breaking any election promises."
During the mining boom WA's share of the GST dropped to 30 cents in the dollar, topped up by federal government funds in what Mr Turnbull called a bandaid solution.
Under the new proposal a 70 cent floor under which no state can fall would be applied from 2022/23, rising to 75 cents from 2024/25.
States and territories are slated to share $67.3 billion in GST payments this financial year, rising to $112.25 billion in 2028/29.
Mr Turnbull again rejected the idea that the GST rate could rise from 10 per cent.
"We're committed to lower taxes," he said.
