You buy a $120,000-face note for $92,000. In the wizard you mark it Purchased → Total, enter the date bought and the $92,000 you paid, and that price becomes your basis. From the first recorded payment, the loan page shows a Yield to Date figure and the Tax Tracking tab grows a Discount Accretion card that splits every principal dollar collected into return of capital and ordinary discount income by the ratio method.
A year in, an investor offers to buy the next $40,000 of principal. You use the guided partial sale: NoteHarbor closes the original as Sold, spawns the buyer's investor piece with the crossing payment prorated to the cent, and spawns your residual. The two schedules add back up to the original, row by row.
At year-end, the org-wide Capital Gains report and Ordinary Income statement roll every disposed and earning note into one view, and the CPA packet exports the closing statement, note, deed, and mortgage with a summary cover sheet. Your accountant gets facts, not a shoebox.