Taxation of pensions: resident state generally has exclusive taxing right, with UN alternatives allowing source-state claims. Pensions for past employment are generally taxable only in the resident State, granting a resident-state taxing right. The UN Model provides Alternative A, under which public social security scheme payments are taxable only in the paying State, and Alternative B, which permits source-state taxation where the payer is a resident or where a permanent establishment or fixed base in the source State incurred and bears the obligation to pay.