Blackstone converted from a publicly traded partnership to a corporation on July 1, 2019. Final schedule K-1s were issued for the year ended July 1, 2019. After the conversion, cash distributions from BX are reported on Form 1099-DIV by the brokerage where your shares are held. If you are trying to access tax information for your investment in Blackstone Funds, please log into BXAccess here or call +1 (800) 262-8138 for assistance.
IRS Form 8937 related to the conversion is available here.
IRS Notice 2019-46 and Notification is available here.