we can't see the agreement between you and the new company but if this is payment for your ownership in the old company, the new company may be misclassifying the payments. apparently, you are not an employee of the new company because the payments should have been on your w-2s. and if you are not performing services for the new company it's probably wrong for them you issue a NEC with the amount in box 1. if the payments are for your ownership in the old company they likely should be treated as capital gain to the extent it exceeded your basis. no SE tax. if there is enough $ involved it may be worth your while to consult a tax pro. there is too much info missing to give a good answer.
however, if you don't want to consult a pro
company name - anything you want - like myoldecomp
business code - 999999
accounting method - cash
