I received 1099B for 2017 from Prosper with several debt sale (no cost basis)and charge-offs . Do I report each entry separately or can I report all as summary?

You will need to report each sale separately or  (if you choose to enter summary entries) you will have to send a copy of your 1099-B to the IRS.  TurboTax will print an 8453 for you if this is your choice, and you will attach the copy and mail it.  If there are only 10-20 entries, I find it easier to enter them manually.

"Cost Basis" is what you paid for your investment.  This information should be on the statement for the period in which you purchased the investment.

I always enter the summary of each sales category instead of going through the pain of adding each entry.  The process usually takes less than 5 minutes for me. You’ll need two pieces of info for each category to be able to do this: proceeds (1d) and cost basis(1e).

Figuring out the proceeds for each category is straight forward, as Prosper lists this at the end of each section (ex: a section with 50 entries for short-term and another section with 100 entries for long-term)

For most people, the painful part is figuring out the cost basis for each category. This is where the following approach can come in handy for folks who have basic computer programming skills:

1 - Copy the text of all transactions in a category from the PDF.

2 - Go to https://regex101.com/

3 - In the ‘Regular Expression’ box enter “Box.1e.+\$?\d+.\d+”

4 - Export all matches as text from ‘Match Information’ Section. This will give you a bunch of rows that look like “Box 1e. $13.58 .”

5 - Copy the entire text and paste it into excel.

6 - Use Find/Replace All to remove all characters that don’t belong to the cost basis: replace “Box 1e. $” with “” (Note: double quotes don’t have to be included.

7 - Select all rows and apply the sum function. Voila!! This sum is the cost basis of the category.

8 - Repeat steps 1 thru 7 for each category.

Hope this helps.