Company Split-off

@Quicken Francisco The comment you linked discusses this issue in Quicken Windows. But this question is about Quicken Mac.

@Henry Theloosen And the problem is that Quicken Mac does not have a transaction/tool/wizard to automatically handle corporate divestitures/spin offs. You may want to visit this Idea post for just such a feature -- and add your vote for it in the yellow box under the first post. If you go down a bit in the thread, a fellow user included his detailed process for handling such a transaction via a temporary account. If you just have one purchase of shares of Merck, it's pretty straightforward; if you have many purchases (including reinvested dividends) over the years, then there can be a bit more adjusting to do.

His approach isn't the only way to do it, and how much work you do depends on how precisely you want your data in Quicken. For instance, are the acquisition dates important to track in Quicken; if you don't sell anything for a year or more, they'll be long-term capital gains whether the shares were acquired today or in 2012; do you care if Quicken shows the correct dates? Will you use Quicken's tax report for your taxes, or the data from your broker's tax forms? Do you want the historical graph in your portfolio to remain exactly accurate, or is that not crucial to you? Some Quicken users wouldn't do anything less than getting every detail mapped out correctly, while others just want to have an up-to-date view of their holdings today and going forward; it all depends how you use Quicken and want to use its data.