Using the self-selection approach to tax analysis, this paper derives
a modified Samuelson Rule for the provision of public goods when the g
overnment deploys an optimal nonlinear income tax. This approach gives
a straightforward interpretation of the central result in this area,
generalises it, and provides a simple characterisation of optimal poli
cy in a wide range of circumstances. The analysis also emphasises and
clarifies the significance of the choice of numeraire for the optimali
ty of ''decentralising'' public spending decisions.