We read this post from Jen - June, 2015:

This mid-year there are tax changes for New Brunswick, Newfoundland, Yukon and British Columbia. No changes in the documentation on the other provinces nor federal changes at this time. Full details are on the official Dynamics GP support blog.

From : https://community.dynamics.com/gp/b/kuntzconsulting/archive/2015/06/03/canadian-payroll-2015-mid-year-tax-update

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Then I get this message from a client here in Alberta - and I am confused.

On June 18, 2015, the Alberta Government announced changes to the Alberta Personal Income Tax Rates. These new rates were to be implemented on October 1.

 Commencing with the first pay date in October 2015, new tax rates, ranging from 12% to 15% will be applied for the remaining 3 (three) months of the year for employees in income tax brackets over $125,000 per year. Employees with income tax bracket less than $125,000 per year will not be affected by this change.

There is no change to the Alberta Personal tax credit/exemption amount (TD1-AB). There are also no changes to the tax rates, income thresholds, or personal tax credit/exemption for Federal or other Provinces/Territories.

 For more information  on this legislative change, please visit the Alberta Treasury Board and Finance departments website where a question and answer document is available: http://finance.alberta.ca/business/tax_rebates/personal-income-tax/personal-income-tax-questions-and-answers.html

Here is an additional piece from the article I found interesting.

Are these changes retroactive?

The new rates and brackets were implemented on October 1, 2015.  However, annual provincial income tax rates must come into effect on January 1 of the respective year, as the personal income tax system only supports annual rates. As a result, lower prorated rates were introduced effective January 1, 2015 to reflect an October 1 introduction of the full rates.

When filing taxes for 2015, tax filers will be assessed based on their total 2015 taxable income and the prorated tax rates. Tax credit and deduction amounts for the 2015 tax year will remain unchanged.

Alberta has asked the federal government to begin administering these changes October 1, 2015. As a result, the withholding tables used by employers will be changed to reflect the new higher rates. The result of this, for those impacted, is that the taxes withheld from individual paycheques after October 1 will reflect the new rates ranging from 12% to 15%. However, the prorated rates for 2015 will appear on the 2015 income tax forms. Updated withholding tables can be found on the Canada Revenue Agency website. The tax rate changes are shown below: