(in Canada)What if my employer doesn't deduct taxes?

I may be starting a new job as a legal secretary, but my employer just pays the hourly rate without deducting anything.

How do I calculate how much to put aside to pay my taxes at the end of the year?

If you are an employee your employer must deduct taxes and EI and CPP premiums.

From the CRA website:

If the worker is an employee, (employer-employee
relationship) the payer is considered an employer.
Employers are responsible for deducting Canada Pension
Plan (CPP) contributions, Employment Insurance
premiums, and income tax from remuneration or other
amounts they pay to their employees. They have to remit
these deductions along with their share of CPP
contributions and EI premiums.
An employer who fails to deduct the required CPP
contributions and EI premiums has to pay both the
employer’s share and the employee’s share of any
contributions and premiums owing, plus penalties and
interest. For more information, visit our Web site at
www.cra.gc.ca/payroll.