There are three types of addendum forms. The first two are UCC1AP and UCC3AP for use when you need to insert additional debtor or secured parties on the UCC1 or UCC3 forms. The third is UCC1AD which is used for real estate related collateral where box 12 must be checked and a legal description must be included in box 14. If the record owner of the real estate is not the Debtor, the name and address of the record owner must be provided in box 15. When the Debtor is a transmitting utility, or a transaction is connected with public finance or a manufactured home, box 18 of the addendum must also be checked.