Key takeaways
- Deductibility of cash-out refinance interest is generally governed by where the proceeds were spent, not by what secures the loan. That principle is the interest tracing framework in Treasury Regulation §1.163-8T.
- A loan secured by a primary residence can produce interest that lands on Schedule A, Schedule E, Schedule C, or nowhere at all — sometimes all in the same loan.
- The tracing clock generally starts when the money is actually spent, not when it funds. Cash-out proceeds parked in a checking account for five months are not characterized until they leave.
- There is no blending. Each dollar of proceeds gets its own character, which is why a single cash-out refinance can require a three-way allocation across schedules.
- With the Q3 estimated payment now behind us and the Q4 installment due January 15, 2027, a client who took cash out this year and assumed the whole payment was deductible may still be underestimating — and the documentation window closes at year-end.
Updated September 18, 2026 with current rate figures and the year-end deadline.
Short answer: the collateral does not determine the deduction. The use of the proceeds does. A cash-out refinance on a San Diego primary residence can generate fully deductible mortgage interest, fully deductible rental interest, deductible business interest, or nondeductible personal interest — and the same loan can generate several of those at once, in proportions set by how the borrower spent the money.
I write this one for the CPAs and tax preparers we work with, because it is the single most common place I see a mortgage and a tax return disagree with each other. The borrower thinks “it is a mortgage on my house, so it is mortgage interest.” The regulation does not care what they think.
Who this is for
This is for CPAs, EAs, and tax preparers with San Diego clients who pulled equity out in the last eighteen months — which, given where local equity sits, is a lot of clients. It is also for the preparer who has a Form 1098 showing $41,000 of interest and a client who cannot clearly account for where $250,000 of cash-out proceeds went.
If that describes a file on your desk, the conversation to have before year-end is not about the 1098. It is about the bank statements.
Why the 1098 is not the answer
Form 1098 reports interest paid on a loan secured by real property. It does not characterize that interest. The lender has no idea what the borrower did with the money and no obligation to find out.
So the 1098 is a starting number, not a conclusion. The characterization work happens downstream, and it happens by tracing.
This matters more after a refinance than after a purchase. On a purchase loan, the tracing is trivial: the money bought the house. On a cash-out, the “rate and term” portion generally inherits the character of the debt it replaced, while the new cash-out portion takes the character of whatever the borrower did with it. One loan, two histories.
The four destinations
Broadly, cash-out proceeds land in one of four buckets. General framework only — the specific treatment of any dollar is a determination for the client’s tax professional.
| What the proceeds bought | Interest character | Generally reported | Common San Diego version |
|---|---|---|---|
| Improvements to the residence securing the loan | Qualified residence interest | Schedule A | ADU build, kitchen, roof, solar |
| Down payment on a rental property | Passive / rental | Schedule E | Pulling equity here to buy out of state |
| Capital for an operating business | Trade or business | Schedule C or the entity return | Self-employed owner funding payroll or inventory |
| Personal consumption | Personal interest | Generally not deductible | Debt payoff, tuition, a car, a wedding |
Note the fourth row, because it is the one that surprises people. Paying off a credit card with home equity does not convert that interest into mortgage interest for deduction purposes. It converts a high rate into a low rate, which is a fine reason to do it — just not a tax reason.
And note the first row’s limit: qualified residence interest is subject to the acquisition-indebtedness cap, which is $750,000 for debt incurred after December 15, 2017. I covered how that cap behaves in San Diego, where loan sizes bump into it routinely, in the mortgage interest deduction post. Tracing decides which bucket; the cap decides how much of the Schedule A bucket survives.
The timing trap
Here is the piece that costs clients the most, and it is a sequencing problem rather than a tax problem.
Cash-out proceeds fund into a bank account. That account already has money in it. The client then spends over the following months from a commingled balance. Six months later, nobody can say with any confidence which dollars were the loan proceeds.
Tracing works on actual expenditures. When the proceeds are commingled and the trail goes cold, the fallback characterization is rarely the favorable one. The fix is embarrassingly simple and has to happen before the money moves:
- Open a separate account for the proceeds. Not a sub-ledger. A separate account. Fund it at closing and spend from it directly.
- Spend it on one thing, or on a small number of clearly documented things. Every transfer out should have an obvious destination.
- Spend it reasonably promptly. The longer proceeds sit, the more likely they mingle with other deposits.
- Keep the closing statement with the bank records. The Closing Disclosure establishes the amount and date; the bank statements establish the use. You need both halves.
When a client tells me they are pulling cash out and they have a CPA, this is the conversation I ask them to have first — not after. It takes ten minutes at the front end and it is unrecoverable at the back end.
Where this shows up in the current market
The 30-year fixed-rate mortgage averaged 6.95% in Freddie Mac’s Primary Mortgage Market Survey dated September 17, 2026, up from 6.76% the prior week; a year earlier it averaged 6.26%. The 15-year averaged 6.26%. That is a fourth consecutive weekly increase, following the Federal Reserve’s quarter-point move on September 16. Those are cited national averages published weekly, not offers or quotes.
Why that matters for tracing: at these rates, very few San Diego homeowners are refinancing purely for rate. They are refinancing for access — to a rental down payment, a business, an ADU. Which means a much higher share of current refinance volume is cash-out, and a much higher share of current refinance volume needs tracing analysis.
The mechanical side of getting equity out is covered in our cash-out refinance walkthrough. If the client’s plan is to redeploy the proceeds into investment property, the 1031 exchange financing piece covers a related structuring question worth raising in the same meeting.
The four questions to ask the client
If you have limited time before year-end, these four get you most of the way:
- Was any of this a cash-out, or was it rate-and-term only? If rate-and-term, tracing is usually straightforward and the prior debt’s character carries.
- What was the cash-out amount, and on what date did it fund? From the Closing Disclosure, not from memory.
- Where did that money go, dollar for dollar? Ask for statements. “Improvements, mostly” is not a traceable answer.
- Did the proceeds sit anywhere first, and did other deposits land in that account? This is the question that determines whether you have a clean trace or a reconstruction project.
When tracing is not the issue at all
Worth saying, because not every refinance needs this workup:
- A pure rate-and-term refinance with no cash out. The replacement debt generally inherits the character of the debt retired. There is little to allocate.
- A client who does not itemize. If the standard deduction wins, the Schedule A analysis is academic — though the Schedule E and Schedule C portions still matter, which is exactly why people miss them.
- Small cash-out amounts spent on documented improvements. Same bucket as the rest of the loan, and the allocation is a formality.
- Proceeds that went entirely to personal consumption. Nothing to trace toward a deduction. Tell the client plainly and move on.
Frequently asked questions
Is interest on a cash-out refinance deductible?
It depends on what the proceeds were used for, not on the fact that a home secures the loan. Proceeds used to improve the residence securing the debt can generally produce qualified residence interest; proceeds used for rental or business purposes are generally traced to those activities; proceeds used for personal consumption generally produce nondeductible personal interest. The client’s tax professional makes that determination on the facts.
Does a home equity line of credit follow the same rules?
The same tracing concept applies — the use of the draw drives the character. Lines of credit are harder to trace in practice because clients draw repeatedly over time and often for mixed purposes. Contemporaneous records matter even more with a line than with a lump-sum refinance.
Can one loan produce interest on more than one schedule?
Yes, and it is common. A $300,000 cash-out split between an ADU, a rental down payment, and paying off a car would generally allocate across three characterizations in proportion to the traced amounts. There is no rule that a single loan gets a single answer.
How does this affect what a client can borrow?
It does not. Tracing is a tax characterization exercise and has no bearing on underwriting, program eligibility, or loan amount. All loans are subject to underwriting review. The two analyses run on separate tracks — which is precisely why they need to be coordinated by someone.
What I would do this quarter
Pull the client list for anyone who closed a refinance in 2026, flag the cash-outs, and request Closing Disclosures plus the sixty days of bank statements that follow each funding date. Do it before year-end, while the Q4 installment and the extension-season files are both still in front of you. Reconstructing a trace in April is expensive; documenting one now is free.
If you would rather have the loan-side facts straight from the file, I am happy to walk a specific transaction with you. The homeowner guide covers the borrower-facing version of the same decision.
Have a client’s refinance you want walked through before year-end?
I will pull the loan structure, the disclosure figures, and the proceeds breakdown so your tracing analysis starts from the actual file instead of the client’s recollection: Book a 20-minute call
Ron Berg is the founder of The Berg Group, a San Diego mortgage team that works alongside CPAs, financial planners, and real estate professionals on the financing side of client decisions. Want the loan facts for a specific file? Book a call.
Sources: Freddie Mac Primary Mortgage Market Survey, survey dated September 17, 2026; Treasury Regulation §1.163-8T (allocation of interest expense); IRS Publication 936, Home Mortgage Interest Deduction; IRS estimated tax guidance.
Ron Berg | NMLS #974839 | C2 Financial Corp, NMLS #135622 | Equal Housing Opportunity. Rates referenced are cited national averages published by Freddie Mac and are not offers, quotes, or commitments to lend. All loans subject to underwriting review; program terms and availability vary. This article is general education for tax professionals and is not tax, legal, or accounting advice. Characterization of interest expense depends on the specific facts of each taxpayer’s situation and should be determined by the taxpayer’s own tax advisor.
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