State supplementary payment
The term “State supplementary payment” means any cash payment made by a State on a regular basis to an individual who is receiving supplemental security income benefits under subchapter XVI or who would but for his income be eligible to receive such benefits, as assistance based on need in supplementation of such benefits (as determined by the Commissioner of Social Security), but only to the extent that such payments are made with respect to an individual with respect to whom supplemental security income benefits are payable under subchapter XVI, or would but for his income be payable under that subchapter.