Employment Contracts and Proof of Salary
All employment contracts are based on trust. However, the employer can demand proof of any information declared in your CV. Though it is taken as an affidavit, many employers require documentary evidence like a payslip to show that you were receiving a certain salary, based on which you were offered the salary by the employer. If you can't produce it, your candidature can be ignored, and somebody else may be hired. You cannot question the legality, but morally, the employer can rely on the declaration or affidavit by the employee that they were receiving this amount of salary. In the case of highly paid employees, they may even ask for previous tax returns.