For 2016, the credit is calculated as follows: 75% of the first $400, 50% on the next $350 and 33 1/3% of any contribution over $750, up to $1,275. This results in a maximum credit of $650. Some provinces provide similar credits against provincial income taxes for contributions made to provincial political parties.
For both federal and provincial purposes, the credit can only reduce taxes paid or payable. If you are not liable for any taxes in 2015, the credit is lost. It cannot be carried forward to 2017. Note that contributions to local mayoral campaigns do not qualify for the political donation tax credit.
Tax tip: Consider spreading your political contributions over two years. For example, if you contribute $750 in 2016, your federal tax credit will be $475. If, instead, you contribute $375 in 2016 and $375 in 2017, your political contribution tax credit will be $281.25 in each of 2016 and 2017, for a total of $562.50.