Interest Tracing Rules for Real Estate Investors (2026)

Almost every real estate investor believes interest is deductible because the loan is secured by a rental property. That is not the rule, and the difference is worth thousands of dollars annually to investors who move money between properties and personal use.

Under Treasury Regulation Sec. 1.163-8T, interest expense is allocated according to how the loan proceeds are used. The collateral is irrelevant.

The Basic Rule

Debt is allocated to expenditures, and interest on that debt takes the character of the expenditure. Proceeds used to buy or improve a rental produce interest allocable to a rental activity, deductible on Schedule E. Proceeds used to buy inventory for a business produce trade or business interest. Proceeds used to buy a boat produce personal interest, which is not deductible at all.

This cuts both directions. A HELOC on your primary residence used to buy a rental property produces interest deductible against rental income, even though the loan is secured by your home and would not qualify as acquisition indebtedness under the home mortgage interest rules.

Conversely, a cash-out refinance on a rental property used to pay off credit cards or fund a vacation produces personal interest, non-deductible, even though the loan is secured by an income-producing asset and appears on the rental's loan statement.

The Ordering Rules When Funds Are Mixed

The regulations provide ordering rules for what happens when loan proceeds land in an account with other money. Under Treasury Regulation Sec. 1.163-8T(c)(4), expenditures from an account containing debt proceeds are treated as made first from the debt proceeds, in the order the proceeds were deposited, for a period of fifteen days.

After that window, a more complex set of rules applies, generally treating expenditures as coming from debt proceeds to the extent of the outstanding balance attributable to those proceeds.

The practical consequence is that commingling creates a tracing mess with results that rarely favor the taxpayer. An investor who deposits $200,000 of refinance proceeds into an operating account, pays personal expenses from that account for four months, and then buys a property is going to have a difficult time establishing that the full $200,000 was traced to the acquisition.

The fix costs nothing. Open a dedicated account. Deposit loan proceeds there. Spend from it only for the intended purpose. This creates an unambiguous trace that survives examination.

The Thirty-Day Rules That Help

Two rules give useful flexibility. Under Treasury Regulation Sec. 1.163-8T(c)(4)(iii)(B), the taxpayer may treat any expenditure made within thirty days before or after debt proceeds are deposited as made from those proceeds.

This matters when the timing does not line up cleanly. An investor who closes on a rental with cash on March 3 and closes a refinance on the prior property March 20 can elect to treat the acquisition as funded by the refinance proceeds, tracing the interest to the rental.

There is also a rule allowing debt proceeds received in cash to be treated as used for personal expenditures on the date received, which is occasionally useful for isolating a personal-use portion cleanly rather than letting it contaminate an otherwise clean trace.

Reallocation When the Use Changes

Debt is reallocated when the proceeds are repaid and reborrowed, or when the underlying asset changes character. If you sell a rental funded by a traced loan and use the proceeds to buy another rental, the debt follows.

If you convert a rental to a personal residence, the interest on debt allocated to that property becomes personal residence interest going forward, subject to the home mortgage interest rules under IRC Sec. 163(h)(3) including the acquisition indebtedness limits.

Under Treasury Regulation Sec. 1.163-8T(c)(1), the allocation of debt is redetermined whenever there is a reallocation event, so this is not a one-time decision made at closing.

Portfolio Loans and Blanket Debt

Investors with blanket loans covering multiple properties, or portfolio lines of credit drawn against several assets, face a harder tracing problem. The loan is secured by everything and funds are drawn as needed.

The answer is the same: trace each draw to its use. A $2,400,000 portfolio line drawn in eleven separate advances over three years produces eleven separate traces, each allocated to whatever the advance funded.

This requires a schedule maintained as you go. Reconstructing it four years later from bank statements is possible but expensive and less reliable. Investors using portfolio debt should maintain a draw log that records date, amount, and use, cross-referenced to closing statements or invoices.

Worked Example: HELOC-Funded Acquisition

An investor takes a $220,000 HELOC on a primary residence and uses $185,000 as the down payment on a $740,000 rental, keeping $35,000 for a kitchen renovation on the primary residence.

Interest on 84% of the HELOC balance, the $185,000 traced to the rental, is deductible against rental income on Schedule E. Interest on the remaining 16% is potentially deductible as home mortgage interest under IRC Sec. 163(h)(3) if the renovation qualifies as a substantial improvement to the residence securing the loan, subject to the acquisition indebtedness limits.

At 8.25% on a $220,000 balance, that is $18,150 of annual interest, of which $15,246 is a rental deduction. Without tracing, an investor might have claimed none of it, treating a HELOC as personal debt, or all of it as home mortgage interest and run into the acquisition indebtedness limit.

The documentation supporting this is the HELOC draw record, the closing statement on the rental, and the renovation invoices. Three documents, held from the start, protect $15,000 of annual deduction indefinitely.

Frequently Asked Questions

Is interest deductible because the loan is secured by a rental property?

No. Under Treas. Reg. Sec. 1.163-8T, interest follows the use of the loan proceeds, not the collateral. A rental-secured loan used for personal expenses produces non-deductible personal interest, and a home-secured HELOC used to buy a rental produces deductible rental interest.

Can I deduct HELOC interest if I used it to buy a rental?

Yes, against the rental. The interest is traced to the rental acquisition and deducted on Schedule E, notwithstanding that the loan is secured by your residence. This is often more favorable than home mortgage interest treatment, which is subject to acquisition indebtedness limits.

What happens if I mix loan proceeds with other money?

Ordering rules in Treas. Reg. Sec. 1.163-8T(c)(4) apply, and they rarely favor the taxpayer. Commingling makes tracing difficult to establish. Deposit loan proceeds into a dedicated account and spend only for the intended purpose. The fix costs nothing and is durable.

Is there any timing flexibility in tracing?

Yes. You may treat an expenditure made within thirty days before or after debt proceeds are received as made from those proceeds. This resolves most real-world timing mismatches between a refinance closing and an acquisition closing.

How do I trace interest on a portfolio line of credit?

Draw by draw. Each advance is traced to whatever it funded. Maintain a draw log recording date, amount, and use, cross-referenced to closing statements or invoices. Reconstructing this years later is possible but expensive and far less defensible.

Interest Tracing Rules: Why Your Loan Security Does Not Determine Deductibility