IBR looks like a mechanical input, one line, one number, plug it into the lease liability formula and move on. In practice it carries more judgement than most people give it credit for. Get it wrong and every downstream number moves with it, the liability, the right-of-use asset, the P&L split between depreciation and interest.
When does the IBR actually apply?
Start with when it actually applies. IFRS 16 says a lessee uses the rate implicit in the lease when that rate can be readily determined, and the incremental borrowing rate when it can't. In practice, "can't" covers most leases, the implicit rate requires knowing the lessor's fair value assumptions and unguaranteed residual value, information a typical corporate lessee rarely has. IFRS defines IBR as the rate a lessee would pay to borrow, over a similar term, with similar security, for an asset of similar value, in a similar economic environment.
Term, security, asset value, economic environment, four constraints collapsed into a single number at a fixed point in time: commencement date for new leases, transition date for anything brought onto the balance sheet retrospectively.
How is the rate built?
The standard doesn't mandate how to get there. What's emerged in practice is a build-up approach: a base rate plus a credit spread. Both legs get matched to the remaining lease term. Term here means more than final maturity, it means a similar repayment profile, since lease payments are periodic, not a single bullet repayment. Currency matters too, both legs sourced in the currency of the lease payments, not the lessee's own functional currency, the two can diverge on cross-border leases. The spread comes from the credit curve or a set of comparable bonds at the relevant tenor and rating. Base plus spread is the default. In cases where a recent issuance by the same borrower exists, it sharpens things further. A recent, comparable issuance, similar in its key terms including seniority, and the spread can be used directly. Significantly different terms, or an older transaction, and the spread instead needs calibrating into a company-specific risk adjustment, layered on top of the general market spread.
Where practitioners diverge: how the credit rating gets built
Where practitioners genuinely diverge is how the borrower's credit rating itself gets built. It largely comes down to data availability. Where the entity has its own recent financing, a bond issuance or a credit facility, the rating and spread can be read directly off that market pricing. Where it doesn't, the alternative is to build a synthetic credit rating from financial ratios, interest coverage, leverage, EBITDA margin, loan to value ratio, mapped against rated peers, then pull market spread data for that notch. The first is more defensible when the data exists, it's entity-specific and observable. The second is the fallback for private companies or anyone without recent debt issuance to point to. Worth naming both, not because one is right and the other wrong, but because an auditor will ask why you picked one over the other.
Why funds are the exception?
One sector where synthetic construction is closer to the default than the fallback: investment funds. Moreover, an SPV lessee inside a fund structure holds a single asset, has no standalone credit history, and carries a balance sheet that may not fully reflect economic reality. Where a guarantor stands behind the SPV, that support should factor into the assessment rather than rating the SPV in isolation.
Does the rate move once it is set?
One thing worth flagging for people coming from a valuation background: IBR doesn't move with the market by default once it's set. Unlike a fair value input that gets revisited constantly, IBR is locked in at commencement and, in most cases, stays there. Some reassessment triggers do call for a revised rate, a change in lease term or a purchase option being one, but the common case, an index-linked rent review, uses the original rate unchanged. Revaluing is the exception, not the routine, which makes it one of the few numbers in lease accounting that gets scrutinised heavily once, then largely left alone.
Which rate applies on reassessment under IFRS 16.40–43. The default is the original rate; a revised rate is the exception.
Both legs of the build-up are data problems before they are judgement problems, which is where a documented source beats a defensible-sounding estimate. The smartZebra interest rate engine covers exactly that ground for lease accounting: risk-free curves by Svensson and Nelson-Siegel for the major currencies, credit spreads calculated for maturities between 1 and 30 years across 15 sectors and 8 sector categories, and a synthetic rating tool that scores an unrated borrower on five areas of credit assessment — with the source timestamp and calculation path behind every number, which is what the auditor's question at the end of the rating discussion actually asks for.
References
- IFRS 16 Leases, para. 26 — the implicit rate if readily determinable, otherwise the lessee's incremental borrowing rate; as endorsed by Commission Regulation (EU) 2017/1986 of 31 October 2017
- IFRS 16 Leases, Appendix A — definitions of "interest rate implicit in the lease" (by reference to the lessor's fair value of the underlying asset, initial direct costs and unguaranteed residual value) and of "lessee's incremental borrowing rate": "the rate of interest that a lessee would have to pay to borrow over a similar term, and with a similar security, the funds necessary to obtain an asset of a similar value to the right-of-use asset in a similar economic environment"
- IFRS 16 Leases, paras. 40–43 — revised discount rate on a change in lease term or purchase option assessment (40, 41); unchanged discount rate on a change in a residual value guarantee or in an index or rate (42, 43), with the floating-rate exception in 43
- IFRS 16 Leases, para. C8(a) — lease liability measured at the lessee's incremental borrowing rate at the date of initial application under the modified retrospective approach
- IFRS 16 Basis for Conclusions, BC161 — the Board's observation that determining the implicit rate is likely to be difficult for lessees, particularly where the underlying asset has a significant residual value
- IFRS Interpretations Committee, agenda decision Lessee's Incremental Borrowing Rate (IFRS 16 Leases), September 2019 — IFRS 16 sets no application guidance on determining the rate; the definition does not explicitly require a rate reflecting a similar payment profile, but referring to such a rate as a starting point is consistent with the Board's objective
Related pages
- Interest Rate Engine: arm's-length rates and credit spreads — yield curves, credit spreads by tenor and sector, and the synthetic rating tool, with IFRS 16 named as a use case
- Cost of Capital — WACC with date-stamped parameters, the same point-in-time discipline the IBR needs
- The Risk-Free Interest Rate in Business Valuation — the base-rate leg: IDW S 1 and the Svensson method
- Determining Market Interest Rates Using the Arm's Length Method — synthetic ratings and spreads for borrowers without observable debt
- Introduction to Loan Valuation and the Private Debt Market — how credit risk is priced where no market quote exists
- For AIFM and fund managers — SPV-level ratings and guarantor support in fund structures
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