YOUR basis per share, assuming that the the alternative valuation date wasn't used, is the (split-adjusted) "fair market value at the Date of Death.
Go here
https://finance.yahoo.com/quote/MFC/history?period1=938156400&period2=1553238000&interval=1d&filter=...
to find that per share value.
I don't think that "stock split before I inherited" explanation holds water. Assuming that you inherited the stock after the stock was being traded publicly - Manulife demutualized in September, 1999 - and and before the 05-25-2006 stock split and simply deposited the shares in your own brokerage account, then the broker, not knowing the history, probably would consider that stock "noncovered" and for a noncovered stock they'd use a basis of $0 on a 1099-B. But a "split" only multiplies the number of shares you own and reduces your basis proportionally, mean your basis in ALL the stock is unchanged. A "split" doesn't magically allow a broker who doesn't know the basis of the pre-split shares somehow magically assign a basis - a basis of only SOME of the shares it would seem - to the post-split shares.
Maybe you were reinvesting the Manulife dividends in new Manulife shares and that's where the "covered" portion is coming from? You need to knuckle down and figure this out so you can properly report the sale.
ASSUMING that my guess is correct and that you've been reinvesting dividends and that's what the "covered" portion of the 1099-B is referring to, you should be able to enter that sale exactly as it reads on the 1099-B.
ASSUMING that the "noncovered" portion of the sale is referring to the original inherited shares deposited in the account, you should be able to enter that portion of the sale exactly as it reads, substituting the correct basis for the incorrect basis when you come to the basis box.
Tom Young
