Contrast approaches to one liability with approaches to a schedule of liabilities, and the different ways each can be implemented

For one liability, immunisation matches Macaulay duration to the horizon. For several liabilities: Cash flow matching buys bonds whose coupons and principal cover each payment; it is safe but costly and inflexible. Duration matching needs asset present value at least equal to liability present value, equal money duration (basis point value), and asset convexity above liability convexity but no higher than necessary. Horizon matching combines the two: cash flow matching for near payments, duration matching for distant ones. Receive-fixed swaps or bond futures can close a duration gap without selling assets. Contingent immunisation lets a manager run an active strategy until the surplus falls to a floor, then immunise. The trap is matching duration alone and ignoring curve twists.