We have had instances where a customer will buy a house to improve and flip and when it matures we renew for 90 or 180 days (because the house isn't ready or didn't sell) with a new note but with the same note number. Going forward, I'm thinking we can't do this because if we have the same loan number will generate the same ULI which can't happen, right?

True renewals are not HMDA reportable. If you're extending the term of the initial purchase and improve note without paying off that obligation, it wouldn't be reportable:

"Thus, except as described in comments 2(d)-2.i and .ii, if a transaction modifies, renews, extends, or amends the terms of an existing debt obligation, but the existing debt obligation is not satisfied and replaced, the transaction is not a closed-end mortgage loan under § 1003.2(d) because there has been no new extension of credit. The phrase extension of credit thus is defined differently under Regulation C than under Regulation B, 12 CFR part 1002."

Assuming it is being satisfied and replaced, you'll need to differentiate the two notes somehow, if not by changing the note number. You could add "a" or "b" to the loan/note combination that you're currently using.

For a refinance, you must use a new ULI. If you extended by a modification, the mod would not be reportable.

The commentary provides guidance on when a ULI can be reused (very limited circumstance):

Paragraph 4(a)(1)(i)

1. ULI—uniqueness. Section 1003.4(a)(1)(i)(B)(2) requires a financial institution that assigns a universal loan identifier (ULI) to each covered loan or application (except as provided in § 1003.4(a)(1)(i)(D) and (E)) to ensure that the character sequence it assigns is unique within the institution and used only for the covered loan or application. A financial institution should assign only one ULI to any particular covered loan or application, and each ULI should correspond to a single application and ensuing loan in the case that the application is approved and a loan is originated. A financial institution may use a ULI that was reported previously to refer only to the same loan or application for which the ULI was used previously or a loan that ensues from an application for which the ULI was used previously. A financial institution may not report an application for a covered loan in 2030 using the same ULI that was reported for a covered loan that was originated in 2020. Similarly, refinancings or applications for refinancing should be assigned a different ULI than the loan that is being refinanced. A financial institution with multiple branches must ensure that its branches do not use the same ULI to refer to multiple covered loans or applications.

Here is where something can change and the ULI remains - the action code will change, you are merely updating the application. If you start over with a new ap, you will have a new ULI.

4. ULI—reinstated or reconsidered application. A financial institution may, at its option, use a ULI previously reported under this part if, during the same calendar year, an applicant asks the institution to reinstate a counteroffer that the applicant previously did not accept or asks the financial institution to reconsider an application that was previously denied, withdrawn, or closed for incompleteness. For example, if a financial institution reports a denied application in its second-quarter 2020 data submission, pursuant to § 1003.5(a)(1)(ii), but then reconsiders the application, which results in an origination in the third quarter of 2020, the financial institution may report the origination in its third-quarter 2020 data submission using the same ULI that was reported for the denied application in its second-quarter 2020 data submission, so long as the financial institution treats the transaction as a continuation of the application. However, a financial institution may not use a ULI previously reported if it reinstates or reconsiders an application that occurred and was reported in a prior calendar year. For example, if a financial institution reports a denied application in its fourth-quarter 2020 data submission, pursuant to § 1003.5(a)(1)(ii), but then reconsiders the application resulting in an origination in the first quarter of 2021, the financial institution reports a denied application under the original ULI in its fourth-quarter 2020 data submission and an approved application with a different ULI in its first-quarter 2021 data submission, pursuant to § 1003.5(a)(1)(ii).