I have question here.Its not necessary.
You can submit the following docs - Offer Letter, Pay Slips, Bank Statements that show your salary being deposited, form-16 if you are from india i.e. You have paid tax on your income, Employer Reference Letter stating your job duties which matches your primary NOC. Salary certificate if you have one and Appraisal letters too if you had one.
Do we need to provide payslips for the whole work period? Thats a lot of pages... For example, my primary work experience is for 5 years. That means I need to provide 60 payslips (5 years x 12 months). Same goes to the bank statements that shows salary deposits.
By the way, OINP requires the proof of only the first and the last month.