If you reside outside Canada and receive a Canadian pension, it is subject to withholding tax when it is paid. The withholding can be up to 25% depending on whether you are in a country that has signed a treaty with Canada.
The CRA has always allowed pensioners to reduce the withholding under certain circumstances. Basically, a calculation is done to reduce the overall tax for the year so that the pensioner would pay tax at the same rate as residents of Canada on the income sourced to Canada including the pension.
To get a reduction in the withholding tax, you needed to apply on an annual basis. Now the CRA is allowing you to apply once every five years.
Of course, you still must file an annual tax return to remain eligible.
CRA’s new form for tax years starting January 2011 can be found here.