Sun Life Financial Inc., expects to a report a third quarter loss of $621 million.

Sun Life Financial, Toronto, Ont., says in a preliminary estimate of its third quarter results, released October 17, that the loss will total $572 million on an operating basis.

Updates to Sun Life’s actuarial methods and assumptions, which generally take place in the third quarter of each year, contributed approximately $200 million to the loss, the company reports.

Sun Life says it will release its full third quarter 2011 financial results on Wednesday, November 2, 2011, after markets close. The company will also host a conference call to discuss its third quarter results on Thursday, November 3, 2011, at 10:00 a.m. ET.