Why do few investors choose off book trading?

External question — Personal Finance Stack Exchange Author: KnowledgeSeeeker Original post: https://money.stackexchange.com/questions/97813 License: CC BY-SA 4.0 — https://creativecommons.org/licenses/by-sa/4.0/ Adaptation: HTML converted to plain text; contact email addresses removed. What is off order book trading and how it is different from order book trading. When I check the 0r1O (LSE), Few websites show $1585.46 ( last order book trade which took place on 22nd of May) and few (e.g. yahoo ) return last price as $1802 which is an off book trade. One more interesting fact I noticed is that Yahoo is returning last close as $1585.46 only which is the last order book trade ( took place on 22nd May ) though there have been continuous off book trades since then. https://www.londonstockexchange.com/exchange/prices-and-markets/stocks/summary/company-summary/US0231351067USUSDSSX4.html https://finance.yahoo.com/quote/0R1O.L?p=0R1O.L Edit: I wonder why few investors prefer off book trading over order book in such above cases. Since the last order book trade ( on 22nd of May ) this security has seen rise of $300 in it's price. Isn't it risky especially with this low amount of trading volume?

External answer — Personal Finance Stack Exchange Author: user6146 Original post: https://money.stackexchange.com/a/164245 License: CC BY-SA 4.0 — https://creativecommons.org/licenses/by-sa/4.0/ Adaptation: HTML converted to plain text; contact email addresses removed. It’s typical for low volumes stocks. There are two parties willing to make a trade at some volume, by doing that off-book they have guaranteed full execution and the price. If they would put their order on the books, partial filling is possible by third party and the remains might not be attractive for either the buyer or seller.