Calkin v CIR [1984] is a very important case because:

a. the case established that an individual can claim losses (i.e. deduct from taxable income) that have resulted from deception, fraud, misrepresentation or theft.
b. the case established that activities constitute a business for tax purposes only if such activities are well-organised.
c. the case established that expenses are not deductible for tax purposes if such expenses are highly unlikely to generate revenue or other gains.
d. .the case established that expenses or other losses are not deductible if the business only exists in the mind of the individual(s) claiming the deductions.