The starting position
The client — a partner in a Chicago professional services firm — owned a Lincoln Park single-family with a $1.6M first mortgage at 5.875%. He wanted to refinance to drop the rate. A national online lender had quoted him 5.50% on a 30-year fixed and told him to apply.
His CPA emailed me before he hit submit. She had two concerns I'd have missed on a quote sheet.
Concern one: the $750K deductibility ceiling
Post-TCJA rules cap home-mortgage interest deductibility at $750,000 of acquisition debt for most filers. The client's original $1.6M mortgage was grandfathered at the pre-2018 $1M cap because the loan predated the law.
The danger: a straight rate-and-term refinance preserves the grandfathered status. A cash-out or restructure can break it — dropping his deductible debt from $1M down to $750K and adding $4–5K per year in real tax cost.
The national lender's quote was structured as a "loan amount adjustment" that would have triggered the break. The CPA flagged it. We restructured to a clean rate-and-term and confirmed in writing with the title company.
Concern two: the 7/1 ARM versus 30-year fixed question
The client's financial advisor was modeling a likely move to Wilmette within 6–8 years. A 30-year fixed locks rate certainty he wouldn't use. A 7/1 ARM at the same lender was priced 0.625% lower.
On a $1.6M loan, that's roughly $10,000 per year in interest savings. Over an 8-year hold, $80K — without the deductibility break.
Concern three: the timing of the close
The CPA had been planning a significant Roth conversion the same year. A large mortgage interest deduction in that tax year would partially offset the conversion tax. Closing the refinance two weeks earlier vs. two months later changed which tax year the deduction landed in — affecting the optimal conversion size.
That's not a rate question. It's not a loan officer question. It's a CPA question that only gets answered if the loan officer is willing to coordinate.
The final structure
- 7/1 ARM at 4.875% (vs. 5.50% on the original quote)
- Pure rate-and-term — preserved $1M grandfathered acquisition debt
- Closed in November — placed the interest deduction in the year of the Roth conversion
- No PMI, no points, lender credit covered closing costs
The math, conservatively
- Rate savings (0.625% on $1.6M, 7 years): roughly $70,000
- Preserved deduction headroom ($250K × ~30% effective rate, 7 years): roughly $50,000
- Roth conversion optimization (CPA-modeled): roughly $28,000
Approximately $148,000 of value over seven years versus the online-lender path. Same client, same property, same rate environment.
None of these decisions involved exotic products. They involved asking the right questions in the right order — and being willing to slow down for a 30-minute call with the client's CPA.
What to take from this
If you're refinancing a jumbo, three questions to ask any lender before you sign disclosures:
- Will this refinance preserve my acquisition-debt grandfathering, if any?
- Have you modeled this against a 7/1 or 10/1 ARM at my expected holding period?
- Are you willing to coordinate with my CPA on closing-date timing?
If the answer to all three isn't a confident yes, you're talking to the wrong lender for this loan.
Bring your CPA. Bring your advisor.
We'll model 2–3 refinance structures, run the deductibility math, and coordinate closing timing with your tax plan.
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