An interest rate swap in general and a type of a seasonal swap in particular, in which the tenor can be altered (extended or shortened) as the counterparty deems fit to his cyclical financing needs. Also, the size of its notional amount is adjustable, though the net present value of the transaction remains unchanged. Owing to the fluctuations in payment at different times, the counterparty, able to alternate between paying fixed and paying floating, can properly match his cash flows.

The concertina swap has many other names of which: accordion swap, NPV swap, rollercoaster swap.