Final answer:
The information on the TD1 form is used by the employer or payer to calculate the federal income tax to deduct from an employee's wages.
Step-by-step explanation:
The information on the federal TD1 is used by the employer or payer to determine the amount of federal income tax to deduct from an employee's wages. The employer uses the information provided on the TD1 form, which includes the employee's personal tax credits, deductions, and allowances, to calculate the appropriate amount of federal income tax that should be withheld from the employee's paycheck.