Updated with 2010 rates! This applies to you if you have a regular job with a salary over about $40,000 per year. We all have to pay CPP and EI, these are deducted at source by your payroll. Both CPP and EI have a maximum annual amount, and that payroll does not spread out the amount throughout the year. The net effect is your take home pay is less at the start of the year, until you reach your maximums.

In 2010, CPP employee contribution rate remains unchanged at 4.95%, and the maximum annual pensionable earnings has gone up from $46,300 to $47,200. If you work it out, with the basic exemption, you have to pay $2,163.15 CPP in 2010. That is an increase of $44.55 or 2% from last year (last year it went up 3%).

For EI, the maximum annual insurable earnings is changing from $42,300 to $43,200 and the EI rate remains unchanged at 1.73% for 2009. If you calculate that, you will need to pay a maximum of $747 for EI in 2010. 

In the above table, you can see that for an income of $50,000 annually, you have reached your maximum at 10.5 months. It was 10.3 months in 2009, so things are continuing to get worse. For some of November and December you get an extra $278 in your pay - just in time for holiday spending or topping up your RRSP.

The more you earn, the sooner you reach your maximum CPP + EI. At a salary of $100,000 you get an extra $557 per month from June through to December. Even more to put into your RRSP...

Pat

P.S. Thanks to the folks who left the comment/correction!