From your comment to another question, I figured out that you're talking about Schedule B of Form 706. 

 (1) Death Prior to Ex-Dividend Date: Dividends declared on stock prior to the date of death, but payable to shareholders of record as of a date after the date of death, are not includable in the decedent's gross estate since the decedent was not entitled to the dividend at the date of death.

(2) Death After Ex-Dividend Date But Prior to Record Date: Under Treas. Reg. §20.2031-2(i), if the decedent acquired stock before the ex-dividend date and the decedent's date of death falls between the ex-dividend date and the record date (Le., the stock is selling "ex-dividend" at the date of death), the listed value of the stock on the decedent's date of death is increased by the amount of the dividend.

(3) Death After Record Date But Before Payment Date: Under Treas. Reg. 20.2033-1(b), if the date of death falls between the record date and the date of payment, the decedent's estate will be entitled to the dividend because the decedent was the shareholder of record on the date of death, Thus, the dividend is listed as a separate Item on Schedule B. 

https://floridafellowsinstitute.org/wp-content/uploads/2020/01/GDK-Anatomy-of-a-706-1-min.pdf