Some common reasons include: 1  a serious accident â such as a road accident, a severe head injury, a serious fall or severe burns. 2  a serious short-term condition â such as a heart attack or a stroke. 3  a serious infection â such as sepsis (blood poisoning) or severe pneumonia.
The definition of unnecessary is not needed. An example of something unnecessary is a bowl of sugar for cooking meatballs.
To be deductible, a business expense must be both ordinary and necessary. An ordinary expense is one that is common and accepted in your trade or business. A necessary expense is one that is helpful and appropriate for your trade or business. An expense does not have to be indispensable to be considered necessary.