The simple answer for most charities is 10% of resources (which includes money, volunteers etc).  However, smaller charities may be able to spend more and charities that have not done political in previous years may be able to spend more in a particular year than 10%.  All political activities of Canadian charities need to be non-partisan and related to the legal objects of the charity.

Here is an excerpt from CRA Guidance on Political Activities – CPS-022

“9. What expenditure limits does the Income Tax Act impose on political activities?

When a charity takes part in political activities, the Act requires that substantially all of its resources must be devoted to charitable activities. The term resources is not defined in the Act, but we consider it to include the total of a charity’s financial assets, as well as everything the charity can use to further its purposes, such as its staff, volunteers, directors, and its premises and equipment.

We usually consider substantially all to mean 90% or more. Any charity using at least this amount of its various resources for charitable work can be assured that we will not revoke its registration on the basis that it is not devoting enough of its resources to charitable activities. Therefore, as a general rule, we consider a charity that devotes no more than 10% of its total resources a year to political activities to be operating within the substantially all provision.

However, we recognize that this may have a negative impact on smaller charities. In an effort to alleviate this hardship, we will exercise our discretion and not revoke the registration of smaller charities for the excessive use of their resources on political activities as long as they meet the following administrative guidelines:
• Registered charities with less than $50,000 annual income in the previous year can devote up to 20% of their resources to political activities in the current year.
• Registered charities whose annual income in the previous year was between $50,000 and $100,000 can devote up to 15% of their resources to political activities in the current year.
• Registered charities whose annual income in the previous year was between $100,000 and $200,000 can devote up to 12% of their resources to political activities in the current year.
Note: These administrative interpretations do not apply for other purposes of the Income Tax Act.

9.1 Averaging a registered charity’s political activities over a number of years

A charity risks revocation if it devotes more than the allowable maximum of its total resources in a fiscal year to political activities. However, infrequent, short-term, one-of-a-kind political activities in excess of this amount will not necessarily disqualify a charity under the substantially all test. For example, an environmental conservation charity may decide to mobilize public support in favour of an international environmental treaty by taking out a full-page advertisement in a national newspaper (thereby devoting more than 10% of its total resources that year to political activities) because it reasonably considers that ratifying the treaty would help the charity achieve its goals.

In such cases, when deciding whether to revoke the charity’s registration, we will consider whether the resources of the charity are still substantially all directed toward its charitable objectives, and if there were unique one-time conditions that led the charity to devote an unusual amount of its resources to political activities. We will determine this by looking at the year under review and comparing it to the charity’s past expenditure patterns and behaviour over one or more previous years. To allow it to overspend in one year, a registered charity can use the unclaimed portion of resources it was allowed to spend but did not spend on political activities from up to two preceding years.

It is therefore extremely important that registered charities complete their annual return, the Registered Charity Information Return (form T3010), as accurately as possible.”

Here is a link to CRA Guidance on Political Activities – CPS-022 http://www.cra-arc.gc.ca/chrts-gvng/chrts/plcy/cps/cps-022-eng.html

As well here is a copy in PDF of the CRA Policy Statement on Political Activities by Canadian Charities CPS-022 – September 2, 2003 so that you can download it easily to your computer.