Online retailer Overstock.com Inc.'s blockchain subsidiary tZERO on Dec. 18 opened a global $250 million initial coin offering to accredited investors, according to a company release.

The offering's presale period will run from Dec. 18 through Jan. 18, 2018, during which tZERO will enter into simple agreements for future equity, or SAFEs, with purchasers identified by the company as accredited investors. During the subsequent sale period, which will run from Jan. 18, 2018, to Feb. 16, 2018, the company will enter into SAFEs with other investors.

Overstock.com, which announced the tZERO security token sale Oct. 24, previously forecast the presale period to begin Nov. 15 and valued the offering at up to $500 million, CNBC reported Oct. 25.

Prospective token holders will not be entitled to any "utility functionality," but the company aims to provide discretionary benefits like discounts on future products and services, and complimentary one-year memberships to Overstock's rewards program for investors buying 100 or more tokens.