Sept 25 (Reuters) - Silver Wheaton Corp said it received reassessment notices from Canada's tax authorities, ordering the mining financing company to pay C$353 million ($264.70 million) in back taxes.

The Vancouver-based company said the notices are consistent with the proposal it had received in July from the revenue agency to tax about C$715 million of income earned by its foreign units between 2005 and 2010.

Silver Wheaton, which will be required to make a deposit of C$177 million with the agency while it pursues a defense, said it intends to file a notice of objection within the required 90 day period.

Silver Wheaton is the world's biggest mining "streaming" company. It pioneered streaming, which involves providing financing to miners for the right to buy a percentage of their future metal production.

The company, whose shares are down more than 30 percent since the announcement of proposed tax charge in July, said earlier this week that it is keen to get its disagreement with Canada's tax authorities to court as soon as possible but any resolution is at least two years away.

($1 = 1.3336 Canadian dollars) (Reporting by Rishika Sadam in Bengaluru; Editing by Anupama Dwivedi)