  We use the known soft and collinear limits of tree- and one-loop scattering
amplitudes -- computed over a decade ago -- to explicitly construct a
subtraction scheme for next-to-next-to-leading order (NNLO) computations. Our
approach combines partitioning of the final-state phase space together with the
technique of sector decomposition, following recent suggestions in Ref. [1]. We
apply this scheme to a toy example: the NNLO QED corrections to the decay of
the Z boson to a pair of massless leptons. We argue that the main features of
this subtraction scheme remain valid for computations of processes of arbitrary
complexity with NNLO accuracy.
