Dow Chemical and DuPont completed their merger to form Dow-DuPont on 9/1/2017. Shares of Dow or DuPont were exchanged for shares of the new Dow-DuPont.
The SEC filing for this merger (S-4A filing of June 7, 2016) was found through the Investor Relations area of the Dow-DuPont web site.  

This is a standard merger. The information below is based on the information available from the S-4A filed with the SEC. Price information is from websites offering historical prices. The data needed is slightly different for Dow and DuPont shareholders.  

The Merger Entry.

Go to Transactions > Merger or Accounting > Securities > Record merger of securities depending on the version of the software being used. If you are unfamiliar with merger transactions you can get help at this URL: https://www.iclub.com/support/kb/default.asp?page=normal_merger  

Here is the information you need to complete the merger for DOW shareholders.

• Date: 9/1/17
• Old Security or Merging Company: Dow (DOW)
• Price per share of old Security / DOW:  66.5
• Cash received:  See your broker statement for cash-in-lieu
• New Security: Dow-DuPont  (DWDP)
• Shares received : 1. x (#of DOW shares owned)
  • (Remember to include fractional shares.)  For example, if you owned 100 DOW shares, you should receive 1.0 x 100 = 100 DWDP shares.
• New Company Price : 66.66  (DWDP opening price on 9/1/2017)

Save the transaction and the merger has been entered.  

Here is the information you need to complete the merger for DuPont shareholders.

• Date: 9/1/17
• Old Security or Merging Company: DuPont  (DD)
• Price per share of old Security / DD:  83.93
• Cash received:  See your broker statement for cash-in-lieu
• New Security: Dow-DuPont  (DWDP)
• Shares received : 1.282 x (#of DD shares owned)
  • (Remember to include fractional shares.)  For example, if you owned 100 DD shares, you should receive 1.282 x 100 = 128.2 DWDP shares.
• New Company Price : 66.66  (DWDP opening price on 9/1/2017)

Save the transaction and the merger has been entered.

NOTE:

Dow and DuPont plan to split the merged company into 3 separate companies within approximately 18 months from the completion of the merger. More to come from them.