1.Sick pay generally means any amount paid under a plan because of an employee's temporary absence from work due to injury, sickness, or disability. It may be paid by either the employer or a third party, such as an insurance company. Sick pay includes both short- and long-term benefits. It is often expressed as a percentage of the employee's regular wages.
Sick Pay는 상해, 병, 불구, 장해로 인하여 종업원이 일시적으로 병가시 지급하는 금액입니다.
고용주가 지급하거나 보험회사가 제 3자가 지급할수도 있겠지요.
2.Sick pay paid by the employer to an employee is wages subject to income tax withholding to the extent the sick pay is includible in the gross income of the employee. ...
 Sick pay paid by an agent of the employer is also wages subject to income tax withholding to the extent includible in gross income.
고용주에 의하여 지급되는 금액 즉 원천징수를 적용한금액은 wage 로 봅니다.
본인 업무와 관련되지 않는 다면 SICK PAY 로 보지않고, 연방고용세 적용대상이 안되겠지요.

3.아래는 SICK PAY에 포함이 안됩니다.
Sick pay doesn't include the following payments.
1. Disability retirement payments. Disability retirement payments aren't sick pay and aren't discussed in this section. Those payments are subject to the rules for federal income tax withholding from pensions and annuities. See section 8.
2. Workers' compensation. Payments because of a work-related injury or sickness that are made under a workers' compensation law aren't sick pay and aren't subject to employment taxes. But see Payments in the nature of workers' compensation?public employees next.
3. Payments in the nature of workers' compensation?public employees. State and local government employees, such as police officers and firefighters, sometimes receive payments due to an injury in the line of duty under a statute that isn't the general workers' compensation law of a state. If the statute limits benefits to work-related injuries or sickness and doesn't base payments on the employee's age, length of service, or prior contributions, the statute is "in the nature of" a workers' compensation law. Payments under a statute in the nature of a workers' compensation law aren't sick pay and aren't subject to employment taxes. For more information, see Regulations section 31.3121(a)(2)-1.
4. Medical expense payments. Payments under a definite plan or system for medical and hospitalization expenses, or for insurance covering these expenses, aren't sick pay and aren't subject to employment taxes.
5. Payments unrelated to absence from work. Accident or health insurance payments unrelated to absence from work aren't sick pay and aren't subject to employment taxes. These include payments for:
a. Permanent loss of a member or function of the body,
b. Permanent loss of the use of a member or function of the body, or
c. Permanent disfigurement of the body.
Example. Donald was injured in a car accident and lost an eye. Under a policy paid for by Donald's employer, Delta Insurance Co. paid Donald $20,000 as compensation for the loss of his eye. Because the payment was determined by the type of injury and was unrelated to Donald's absence from work, it isn't sick pay and isn't subject to federal employment taxes.

1) 즉, SICK PAY( Taxable)  와 Compensation for Injury & Sickness( Non Taxable) 개념은 완전히 다른 개념입니다.
2) Compensation for Injury & Sickness가 Nontaxable로 처리되는 이유가 'better economic position에 있게 되므로'라고 써있습니다.  better economic position 으로 복ㅈ비차원으로 생각하셔야 합니다. IRS 입장에서보면, 병가로 인한지급은 이런정도는 IRS  정부 복지 차원에서 비과세로 봐준다고 봐야 합니다.