Schedule D. When is it not required? I have capital loss carryover. Third party designee number?

The IRS instructions for Schedule D list the following reasons that Schedule D is required.

• To figure the overall gain or loss from transactions reported on Form 8949;
  
• To report certain transactions you don't have to report on Form 8949;
  
• To report a gain from Form 2439 or 6252 or Part I of Form 4797;
  
• To report a gain or loss from Form 4684, 6781, or 8824;
  
• To report a gain or loss from a partnership, S corporation, estate, or trust;
  
• To report capital gain distributions not reported directly on Schedule 1 (Form
  1040), line 13 (or effectively connected capital gain distributions not reported directly
  on Form 1040NR, line 14); and
  
• To report a capital loss carryover from 2017 to 2018.

Schedule D is not required if none of the listed reasons apply. It is not required if your only capital gains are capital gain distributions reported in box 2a of Form 1099-DIV (unless one of the reasons listed above also applies). Note that Schedule D is required if you have a capital loss carryover (the last bullet in the list above).

Schedule D has nothing to do with a third-party designee. A third-party designee is entered on Schedule 6.