Normal Course Issuer bid limitsSee:
https://www.tmx.com/en/pdf/Policy5-6.pdf (which applies to the Venture exchange, but I think it's the same for the TSX). Under a Normal Course Issuer Bid, a company can buy up to 10% of the outstanding shares. If they want to purchase more, they need to make a Substantial Issuer Bid. If I understand correctly, the intention is to prevent companies from manipulating their share price. They can buy up to 10% of their shares (with advance notice) as part of the normal course of business. But if they want to buy more, they have to say something like: we offer to buy 300 million shares at $1.50 per share and let everyone tender their shares. If 400 million shares are tendered, they would buy 3/4 of the shares that each investor tendered. Since Yellow is running out of buying room in some of their NCIBs, I wouldn't be surprised to see some SIBs soon.