For the first box "More than one employer or payer at the same time", if you already filled out the TD1 and TD1ON forms in your first job, it means that you already claimed your personal tax credit and you can not claim again so you will need to check this box.
After calculating your estimated total income in the current year from all income sources (both two part-time jobs in your case), if that amount is less than the basic personal amount "10,880" in TD1 form or less than "13,808" in TD1ON form, you will need to check the second box "total income less than total claim amount" for both forms and your employer will not deduct federal tax and Ontario tax from your gross earnings.
For calculating your estimated total income in the year when you become an employee, you can use this formula to calculate your estimated income: Your current income multiplies your total payroll period in a year. For example, if your payroll period is weekly (52 paid per year) then your estimated income in a year will equal your current income multiplies "52", similar with bi-weekly (26 paid per year), semi-monthly (24 paid per year), and monthly (12 paid per year) payroll period.
For any further information, please feel free to discuss with us.
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