Does anyone know who my financial institution would be on 1099-INT letter? This is my first time receiving this letter and I am a bit confused.

Your financial institution is the bank or brokerage that sent you the letter, which you have an account with.

Look for the Payer's name on Form 1099-INT. That's the financial institution.

You should also see a Payer's TIN which is the tax ID number.

is the letter from the IRS/US Treasury.  then use IRS or US Treasury for the name of the financial institution.  the iRS was late in paying some refunds. interest was owed. the IRS should have sent 1099-INT but some taxpayers report receiving a letter.   just make sure you're not duplicating an entry.