Trying to calculate the amount of tax someone needs to pay based on age

This is my current code, and I'm trying to calculate the amount of tax someone needs to pay based on their age. The calculations are right, but I keep getting errors.

    #Get the Age of from user input
    from datetime import datetime, date
    
    print("Please enter your date of birth (dd mm yyyy)")
    date_of_birth = datetime.strptime(input("--->"), "%d %m %Y")
    
    def calculate_age(born):
        today = date.today()
        return today.year - born.year - ((today.month, today.day) < (born.month, born.day))
    
    age = calculate_age(date_of_birth)
    
    print("You are " ,int(age), " years old.")
    
    #Get the Salary from user input
    def get_salary():
        while True:
            try:
                salary = int(input("Please enter your salary: "))
            except ValueError:
                print("You need to enter a number ")
            else:
                break
        return salary
    
    #Calculate the Amount that needs to be paid, using if,elif,else
    def contribution(age):
        if age <= 35:
            tax = (salary * 0.20)
        elif 36 <= age <= 50:
            tax = (salary * 0.20)
        elif 51 <= age <= 55:
            tax = (salary * 0.185)
        elif 56 <= age <= 60:
            tax = (salary * 0.13)
        elif 61 <= age <= 65:
            tax = (salary * 0.075)
        else:
            tax = (salary * 0.05)
    
        return tax
    
    #Print the amount 
    if __name__ == "__main__":
        salary = get_salary
        tax = contribution(age)
        print("you have to pay", tax, " every month.")
    

This is the error that keeps popping up:

Please enter your date of birth (dd mm yyyy)
--->01 08 1946
You are  74  years old.
Traceback (most recent call last):
  File "/Users/mikael/Age-TaxCalculator.py", line 46, in <module>
    tax = contribution(age)
  File "/Users/mikael/Age-TaxCalculator.py", line 39, in contribution
    tax = (salary * 0.05)
TypeError: unsupported operand type(s) for *: 'function' and 'float'
>>> 

When the program ends, I would like it to prompt the user if he/she needs to do another calculation. After researching for hours trying to find a solution, do I move the whole main code into this function?

while True:
    #input the whole code
    while True:
        answer = str(input("Do you need to do another calculation? (y/n): "))
        if answer in ("y", "n"):
            break
        print "invalid input."
    if answer == "y":
        continue
    else:
        print("Thank you, Goodbye")
        break