It can be seen, on an analysis of Section 15, that for the said Section to apply, there should be a vested right in an employee to claim any salary from an employer or former employer, whether due or not if paid; or paid or allowed, though not due. In CIT v. L.W. Russel reported in 53 ITR 91 (SC), this Court dealt with the provisions of Section 7(1) of the 1922 Act, which preceded Sections 15 and 17 of the present Act and held that it is necessary for the employee to have a vested right to receive an amount from his employer before he could be brought to tax under the head “salaries”; Tips being purely voluntary amounts that may or may not be paid by customers for services rendered to them would not, therefore, fall within Section 15(b) at all. Also, it is clear that salary must be paid or allowed to an employee in the previous year “by or on behalf of” an employer. Even assuming that the expression “allowed” is an expression of width, the salary must be paid by or on behalf of an employer. It must first be noticed that the expression “employer” is different from the expression “person”. An “employer” is a person who employs another person under a contract of employment, express or implied, to perform work for the employer. Therefore, Section 15(b) necessarily has reference to the contract of employment between employer and employee, and salary paid or allowed must therefore have reference to such contract of employment.