A swap (interest rate swap, cross-currency swap) which initiates or kicks in at a forward start date which coincides with the date at which an existing swap with similar terms terminates. Therefore, the latter swap effectively extends the term of the previous swap. This swap gives one of the counterparties the right to extend the maturity date of the swap on the same terms for a pre-agreed additional term. The structure consists of a vanilla swap for the initial term combined with a long swaption for the extension, with the swaption premium incorporated to the cost of the swap.

It is also known as an extendable swap.