It is very important for the retirees to know whether their pensions are taxable or not. If social security is the only source of sustaining then it is not taxable but if your social security has other additions like tax-exempt interest, exempt from savings bond interest, side job or a foreign-earned income is greater than your base amount then more than half of your pension will be taxed. In such cases there is an advantage that you can fill in a Form W-4V, Voluntary Withholding Request that would withhold a certain percentage of income from the total income from being taxed.