Common stock. Only common stock, either voting or nonvoting, in a domestic corporation may qualify as section 1244 stock. For purposes of section 1244, neither securities of the corporation convertible into common stock nor common stock convertible into other securities of the corporation are treated as common stock. An increase in the basis of outstanding stock as a result of a contribution to capital is not treated as an issuance of stock under section 1244. For definition of domestic corporation, see section 7701(a)(4) and the regulations under that section.