Most note investors come to servicing from the other side of a closing table. You did not write these loans. You bought them, from an originator winding down a book, from a fund selling a tape, or one at a time from a seller who carried the paper and wanted cash instead. Usually you paid less than the balance. Sometimes you bought only a slice.
That is a different job from originating, and almost every servicing tool was built for originating. It will hold your notes and post your payments perfectly well, and then go quiet on the four questions that are the entire reason you bought at a discount in the first place.
This is about those four questions, and why a bought book needs answers an originated one never asks for.
The difference, in one sentence
An originator services the note. An investor services the purchase.
The note is the borrower's obligation: a balance, a rate, a schedule. Origination software models that faithfully, and if you paid face value for it, that model is also yours. The moment you pay something other than face, a second set of numbers appears on top of the borrower's, and it belongs to you alone. What did the note cost you. What is it earning on that cost. How much of each payment is your money coming back versus income you made on the spread. None of that lives in the borrower's schedule, because the borrower does not know or care what you paid.
A tool that only knows the note knows half of a bought book.
What origination software gets right
Worth saying plainly, because for one kind of buyer the answer is genuinely "carry on".
If you buy performing notes at or very near face, hold them to term, and hand a tidy spreadsheet to a CPA who is happy with it, the borrower's schedule really is your schedule, and a general servicing tool covers you. The costs below do not scale with how many notes you own. They scale with how far your price sat below face, whether you bought whole notes or pieces, and whether you ever intend to sell. Here is where those parts start moving.
Question one: what did you actually pay for
You bought a note with a $120,000 balance for $92,000. The borrower still owes $120,000 and still pays on it. But your basis is $92,000, and that number, not the balance, is what every other figure has to be measured against.
It changes the character of the payments you collect. Once you have bought below face, a principal dollar the borrower pays is partly a return of your $92,000 and partly income, the discount you earned turning into money. The IRS treats a discount bought in the market, described in Publication 550, Investment Income and Expenses at irs.gov, as generally ordinary income, recognized as it accrues if you so elect or otherwise as ordinary gain on disposition to the extent of the accrued market discount under Internal Revenue Code section 1276. Whether a particular note is a market discount bond, and how the discount is characterized on your return, is a determination your CPA makes on the facts, not one a servicing tool makes for you.
What the tool owes you is the split, cleanly and from the real payments. NoteHarbor records the acquisition with the price paid as basis, and the Tax Tracking tab grows a Discount Accretion card that divides every principal dollar collected into return of capital and ordinary discount income by the ratio method. Your accountant characterizes it. You should not be reconstructing it in a spreadsheet in April.
Question two: what is the note really yielding
The coupon on that note might be 9%. Your yield is not 9%, because you did not pay $120,000 to earn it. You paid $92,000, and the payments that 9% coupon throws off are landing on a smaller number, so your real return is higher, and the gap is the whole point of buying at a discount.
Coupon is the borrower's rate. Yield is what your cash earns, and the only honest way to state it is an internal rate of return over the actual cash flows: the price you paid on the day you paid it, against every payment on the day it lands. NoteHarbor computes exactly that, an annualized XIRR on an Actual/365 basis, and shows it as Yield to Date while the note is open and Realized Yield once it closes. Escrow is excluded because it is not your money, and when a note has too few flows to solve for a rate the figure is left blank rather than guessed. Across the book, the Yield Report ranks every note by that real number and exports to CSV, with an honest coverage line for the ones it cannot yet compute.
Before you buy, the arithmetic is the same in reverse: pick a yield and solve for the price that earns it. You can size an offer on a discounted note with the free discount-bid calculator, which is public and stays that way, and the in-app Deal Analyzer prices a Full, Partial, or B-Schedule purchase with the same math the position cards use after you own it.
Question three: you bought a slice, not the borrower
Note buying has a move originating does not: you can buy part of a note. The next sixty payments, or a face-rate B-schedule behind someone else's position, without buying the borrower's whole stream. It is one of the most useful things an investor can do, and it is precisely where borrower-shaped software falls over, because there is no borrower whose schedule matches what you bought.
A partial needs its own ledger. NoteHarbor gives a partial purchase an investor-position ledger that amortizes your basis at your own yield alongside the payor's unchanged schedule, so you can see your piece and the borrower's obligation side by side and watch the crossing payment split to the cent. A B-schedule purchase runs a triple ledger, where the discount is not recognized until payoff. And both are deliberately held out of the portfolio's weighted averages, so a slice you own never distorts the WAC, WAM, and basis-weighted yield of the notes you own whole. The mechanics of recording a purchase, whole or partial, are in buying notes.
Question four: the number your CPA actually needs
Everything above converges in the worst month for it. A bought book generates three kinds of taxable event an originated one does not, and if the numbers are not already separated, someone separates them by hand under a deadline.
There is the ordinary discount income from question one, accruing as principal comes back. There is capital gain or loss when you sell or a note pays off, long-term or short-term depending on how long you held it, the one-year line the IRS draws in Publication 550. And there is the case that trips people: when you sell a note that is itself a seller-financed installment obligation, disposing of it is generally a taxable event under IRC section 453B, described in Publication 537, Installment Sales, and the Form 6252 instructions at irs.gov, not something that quietly passes to the buyer at face.
NoteHarbor keeps these apart from the ledger you already service against. The Ordinary Income statement separates interest, fee, and discount income from return of capital. The Capital Gains report is Schedule-D-shaped and classifies each disposition long- or short-term by holding period. The guided note sale recognizes the remaining section 453B deferred gain with a basis of the outstanding balance times one minus the gross profit percentage, rather than booking the sale at face. None of it is a filed number, all of it is a clean handoff, and the capital gains and ordinary income reports show what your accountant receives. When you are done, the CPA packet bundles the closing statement, note, deed, and mortgage into a ZIP with a summary cover sheet.
When a bought book does not need this
The honest off-ramp, because it is real. If you own a handful of notes bought at or near face, none of them partials, you are not planning to sell, and your CPA already has a spreadsheet they trust, the discount is small enough and the structure simple enough that the extra ledgers earn nothing. Basis roughly equals face, yield roughly equals coupon, and there is no §453B event on the horizon. Keep the spreadsheet. The four questions above only bite once the discount is meaningful, the positions get sliced, or a sale is in view, and they bite hardest on a book that grew into that without noticing.
Where NoteHarbor sits
Stated plainly so it can be held against any other answer.
It is a system of record for notes you bought, servicing them on what you paid rather than on their face. You record each acquisition as Originated, Total, Partial, or B-Schedule with your price as basis, and from there the real yield, the discount split, the position ledgers, and the tax cards derive from the payments you actually post, in integer cents through a tested engine. It does not hold or move money and no funds pass through it: the investor and lienholder positions it tracks are bookkeeping over money you moved yourself. Bringing a portfolio over is free, with a guided CSV import that reads an export from Moneylender Pro, NoteSmith, or a generic spreadsheet, auto-maps the columns, previews what it will create, and imports at each note's current balance.
The note investor overview is the product version of this article, feature by feature. If your book is more originated than bought, loan servicing software for private lenders and what a loan tracker will not do come at the same engine from the lender's side. If you want to test the four questions above against notes you actually own, the trial is 14 days with no card.
The short version: origination software is not wrong about your notes, it is silent about your purchase, and the purchase is the part you are being paid to get right.
This article is general information, not legal, tax, or accounting advice. Whether the market discount rules, the installment sale rules, or a §453B disposition apply to a given note, and what you owe on it, depend on facts specific to you and the instrument. The tax figures above are accurate as of September 2026 and change. Talk to a licensed CPA about your own book.