Hi, I had an investment in a company that made short term loans to small businesses. This Company went bankrupt in August 2018. How to report loss?

You deduct this as an investment loss and enter it in the investment section of TurboTax.  

Since it became worthless in 2018 (year of bankruptcy), you'll need to amend your 2018 income tax return(s).

• See How to amend (change or correct) a return you already filed.

Enter a worthless investment with the proceeds (sales price) of zero and the word "worthless" in its description. Enter the correct cost or basis, date acquired, and December 31 as the date sold if you don't have a definite date it became worthless. 

Non-security investment sales are entered as follows: 

1. Open (continue) your return in TurboTax.
2. In the search box, search for investment sales then click the "Jump to" link in the search results.
3. Answer Yes to the question Did you sell any investments?
   • If you land on the Here's the investment sales we have so far screen, click Add More Sales.
4. Answer No to the 1099-B question.
5. On the Now we'll walk you through entering your sale details screen, select other, I purchased it, name of corp. Continue entering making sure to enter $0 as Proceeds. 
6. Continue following the onscreen instructions until complete.

Note: You can deduct a net loss of up to $3,000 ($1,500 if married filing separately). Any capital loss you couldn't deduct this year can be carried forward and deducted on future tax returns as a capital loss carryover.