I paid interest to a private party on a loan that I used for a real estate joint venture. The interest was just under $3000. Do I need to complete a form to give them?

Yes, you do need to issue form 1099-INT, since you paid more than $600.  

You must issue the form to whom you paid at least $10 of interest  (or at least $600 of interest paid in the course of your trade of business) per IRS 1099-INT instructions.

The question was: What if the Payor never sent a 1099-int on interest paid on a note secured by real estate ? Amount approx $7,000. Without a 1099-int, how to verify the amount to be reported on scheduler's. B

Appoximately $7,000 of interest received from a private party due on a note secured by real estate BUT, no 1099-int was sent by the payor. How duo we prove the exact amount ?

You should have an amortization schedule showing the amount of interest and principal for each payment you received.

From the amortization schedule you can determine the exact amount of interest your received during 2019.

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