Get your taxes done using TurboTax

You don't actually show the loan itself in your business tax return.  Loan repayments are considered debt service, but the interest is deductible as a business expense.  Since you didn't have any interest payments before the year of the return, there is no need to amend prior years' returns.

You can deduct the finance charges under Other Common Business Expenses, using these steps

1. Click on the Business tab > Continue > I'll choose what to work on
2. On the Let's gather your business info screen, in the Business Income and Expenses section, click the Start/Update button.
3. If you have already started adding information about your business, you will see the screen Here’s the business info we have so far.  Click on the Edit box next to the business.
4. If you haven't yet started adding business information, continue through the screens to enter the needed information.
5. You will now be on the Your [XX] Business screen. 
6. In the Business Expenses section, click the Start/Update box next to Other Common Business Expenses.
7. On the next screen, click the Start box next to Interest Payments.
8. Continue through the screens, entering the requested information.
   

[Edited | 4/15/2020 | 1:10pm PDT]