The independent Parliamentary Budget Office has found the Greens' key revenue-raising proposals would raise $43 billion for federal budget coffers over the next four years.

As Greens leader Christine Milne launches the party's national policy platform on Sunday, the budget office has costed the party's figures for its major revenue-raising initiatives.

Greens leader Christine Milne.

The office found $42.7 billion would be raised by the Greens' proposed levy on the big banks, its mining tax restructure, ending tax breaks to "big miners", abolishing funding for so-called clean coal technology and increasing the marginal tax rate on incomes above $1 million.

The Greens say they would use the money to inject more cash into the school funding reforms and boost funding for Newstart, overseas aid, regional arts and the homeless.