The phrase "additional interest" refers to an extra amount of interest that is added to the original interest being paid on a loan or investment. It means that you will need to pay or receive more money on top of what was initially agreed upon.
Your landlord can be listed as additional interest on your policy. (effectivecoverage.com)
Make sure to list the landlord as additional interest on your renters insurance, not as additional insured. (effectivecoverage.com)
Just one missed payment on your credit report can decrease your credit score by 90 - to 110 - points and mean thousands in additional interest payments on new loans. (peerfinance101.com)