To calculate the incremental borrowing rate for a lease, you construct a hypothetical loan that mirrors the lease’s economics — its term, currency, collateral assumption, and your own credit profile as of the commencement date — and then derive the rate that loan would carry. Under both ASC 842 and IFRS 16, this synthetic rate is what a lessee uses to discount future lease payments whenever the rate implicit in the lease is not readily determinable, which is almost always the case.1DART – Deloitte Accounting Research Tool. Chapter 7 — Discount Rates – 7.1 General
What the Two Standards Actually Ask For
ASC 842 defines the IBR as the rate a lessee would pay to borrow on a collateralized basis, over a similar term, an amount equal to the lease payments in a similar economic environment.1DART – Deloitte Accounting Research Tool. Chapter 7 — Discount Rates – 7.1 General IFRS 16 defines it as the rate a lessee would pay to borrow, over a similar term and with similar security, the funds necessary to obtain an asset of a similar value to the right-of-use asset in a similar economic environment.2IFRS Foundation. Lessee’s Incremental Borrowing Rate (IFRS 16)
The practical difference sits in the loan size. ASC 842 sizes the hypothetical loan to the total lease payments. IFRS 16 sizes it to the value of the underlying asset. For most leases the two amounts are close enough that the resulting rate barely differs. But when an asset’s fair value materially exceeds the payments — think a short lease on expensive equipment — the IFRS 16 version can produce a meaningfully different rate. Know which standard governs your reporting before you start.
The Five Inputs That Define the Rate
A single company-wide rate applied across every lease will not satisfy either standard. Each lease has its own risk profile, and the IBR has to reflect it. Five inputs do that work.
- Lease term. The length of the hypothetical borrowing matches the lease term. A 10-year lease carries more duration and credit risk than a two-year one, and the rate for the longer term is generally higher.
- Currency. If payments are in a foreign currency, the IBR reflects borrowing costs in that currency. Sovereign risk and the local rate environment can push the number well above or below your home-currency cost of funds.
- Credit profile. Your creditworthiness is the single biggest driver of the spread above the risk-free rate. An investment-grade entity will land a much lower IBR than a speculative-grade borrower.
- Collateral. Under ASC 842, assume full collateralization, not under- or overcollateralization. The collateral does not have to be the leased asset itself; it can be any form a creditor would accept for a loan of similar term, as long as it is at least as liquid as the leased asset.1DART – Deloitte Accounting Research Tool. Chapter 7 — Discount Rates – 7.1 General
- Economic environment at commencement. The rate is anchored to market conditions on the lease commencement date. Otherwise identical leases signed two years apart can carry very different IBRs.
Generalizing any of these is the fastest way to a rate that neither reflects the lease’s actual risk nor holds up under audit.
Subsidiary or Parent Credit
When a subsidiary is the lessee, the default is to use the subsidiary’s own creditworthiness. Many corporate groups, though, manage borrowing centrally at the parent. If the parent guarantees the lease, or if the lessor priced the deal off the parent’s credit rather than the subsidiary’s, the parent or consolidated group IBR can be the right rate. ASC 842 includes an example concluding that a subsidiary should use the parent’s IBR when treasury is centralized and the parent’s credit profile more significantly influenced the lease pricing than the subsidiary’s own standing.
Pick a Calculation Method
No single formula produces the IBR. Most entities use one of three approaches, or combine them, depending on the data available.
Start From Existing Debt
If you have recently issued bonds or drawn on a bank facility with a comparable term, that rate already bakes in your credit risk and the current market. It is a natural starting point. The work is in the adjustments. If your existing debt has a shorter maturity than the lease, push the rate up to reflect the additional duration risk. If the debt is unsecured but the IBR assumes full collateralization, adjust downward to reflect the lower risk a secured lender faces. Quantifying those adjustments takes judgment, but you are building from an observable internal data point rather than modeling from scratch, which is easier to defend.
Use a Credit-Rating Yield Curve
Without recent comparable debt, published yield curves fill the gap. Market data providers plot yields against maturities for each credit-rating tier — A, BBB, and so on. Read the yield off the curve matching your rating at your lease term. That yield reflects unsecured borrowing, so apply a downward adjustment for the collateralization assumption. This method suits public companies with established ratings and produces a rate anchored to observable market data, which strengthens its audit defense.
Build Up From the Risk-Free Rate
Private companies or entities without a formal rating usually build the rate from the bottom. Start with the risk-free rate, typically the yield on a government bond matching the lease term. Add a credit spread derived from spreads on comparable-rated companies in the same industry. Apply a final adjustment for the collateral effect. Three layers, one customized IBR, no need for public debt history.
Shortcuts Worth Knowing
Portfolio Approach
Calculating a unique rate for every one of hundreds of leases can be impractical. ASC 842 lets a lessee apply a single discount rate to a group of new leases entered into during the same period, provided the leases share similar terms and both the lessee’s credit rating and the interest-rate environment held steady over that period.3Deloitte Accounting Research Tool. 7.2 Determination of the Discount Rate for Lessees
The result cannot materially differ from what a lease-by-lease calculation would produce, so the grouping matters. Sensible attributes for stratification include lease term, type of underlying collateral, and payment size. A batch of 400 four-to-five-year office leases signed in the same quarter can reasonably share one rate. A mix of two-year copier leases and 15-year warehouse leases cannot.3Deloitte Accounting Research Tool. 7.2 Determination of the Discount Rate for Lessees
Risk-Free Rate Election for Private Companies
Entities that are not public business entities have a simpler path. FASB ASU 2021-09 lets these lessees elect the risk-free rate as their discount rate instead of calculating a full IBR.4FASB. Leases (Topic 842) – ASU 2021-09 The election can be made by class of underlying asset, so a company might use the risk-free rate for vehicle leases and calculate a traditional IBR for real estate leases.
The risk-free rate is easier to determine and defend because it uses published government bond yields with no credit-spread analysis. The trade-off: it is lower than any entity’s actual borrowing cost, which produces a higher lease liability on the balance sheet. For lessees whose balance sheet optics matter, the administrative savings may not be worth it. The election must be disclosed, including which asset classes it covers. And if the rate implicit in a specific lease is readily determinable, that implicit rate still takes priority.4FASB. Leases (Topic 842) – ASU 2021-09
When the Rate Has to Be Recalculated
The IBR set at commencement does not carry unchanged through every future period. Certain events require remeasurement of the lease liability, and some of those events also require refreshing the discount rate.
Under ASC 842, remeasure the liability and update the rate when the lease term changes — for example, when you become reasonably certain to exercise a renewal option you previously expected to decline — or when your assessment of a purchase option changes. The updated rate is the IBR as of the remeasurement date, not the original commencement date. Lease modifications that change scope or consideration and are not treated as separate new leases also require a revised rate determined at the modification’s effective date.
Under IFRS 16, a change in payments resulting from a change in a floating index or rate triggers remeasurement of the liability, but the treatment of the discount rate differs by event: some remeasurements refresh the rate, others retain the original. The specific triggering event determines the treatment. Simple index-driven variable-payment adjustments under ASC 842 do not update the rate at all — the original commencement rate stays in place. Mapping each event to the correct rate treatment before booking the entry avoids over- or understating the liability.
Document Enough to Defend the Number
A defensible calculation is only as strong as its documentation. Auditors expect a written methodology, sometimes called an ASC 842 IBR report, that walks through the inputs, the data sources, the calculation method, and every adjustment. Align on methodology with your auditor before finalizing the rate. Reconstructing the rationale months later is painful and rarely convincing.
At a minimum, the file should show the starting rate and its source, the lease-specific inputs (term, currency, credit profile, collateral type), each adjustment and its basis, and the final calculated rate. For a portfolio approach, add how leases were grouped and why the grouping produces results materially consistent with a lease-by-lease result.
On disclosure, ASC 842 requires the weighted-average discount rate to be reported separately for operating and finance leases.4FASB. Leases (Topic 842) – ASU 2021-09 Lessees also disclose the significant judgments made in applying the standard, which includes the approach used to determine the discount rate.5Deloitte Accounting Research Tool. Lessee Disclosure Requirements SEC registrants have drawn staff comment letters asking them to clarify whether the rate implicit in the lease was readily determinable and to explain the basis for using the IBR instead.