I know of no "requirement" for this. I would, however, consider it a best practice. Such a worksheet helps to document financial analysis (i.e. cash flow, debt to income, etc.); policy compliance (i.e. collatral values, loan to value, amortization, etc.); the intent of the officer (for example, the loan might be a six month single pay, with an expected 10% reduction at maturity...this would not generally be noted on the note itself and must be documented somewhere); the borrower's total relationship; etc. If a loan officer leaves or the loan is otherwise reassigned to another officer, such worksheets provide a good starting point for the new officer to get to know the customer relationship. Worksheets are also nice for loan review, auditors, and examiners.
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My opinions are just that...my opinions.