A common error in Saudi WACC models is applying a foreign after-tax debt formula without first checking whether the same interest deductibility applies to the entity being valued.
Get this wrong and WACC is understated - sometimes meaningfully.
The Standard Textbook Formula
WACC = (w_e × K_e) + [w_d × K_d × (1 − t)]
This formula assumes a corporate income tax shield: that interest expense reduces taxable income, making debt financing cheaper than its face cost.
Practical Modeling Defaults for Saudi Entities
| Entity Type | Default Treatment | Rationale |
|---|---|---|
| Income tax payer | K_d × (1 − t) | Standard tax shield applies |
| Zakat payer | K_d (pre-tax) | Conventional interest deduction not established |
| Mixed structure | Weighted blend | Document clearly with entity-level detail |
For Zakat payers, the conservative and defensible default is to treat K_d at its full pre-tax rate, unless you have specific, documented evidence that an interest tax shield is available to the entity.
Mixed Structures
Some Saudi entities pay both Zakat and corporate income tax - for example, companies with foreign ownership stakes above certain thresholds. In these cases, you can approximate an effective shield factor and apply it to K_d. This must be grounded in the entity’s actual structure and supported by qualified tax advice where required.
Why Sensitivity Is Mandatory Here
The difference between assuming a full tax shield and assuming none can be 50–100 basis points in WACC. That is not a rounding error - it is a material valuation input.
Show WACC under both assumptions and present valuation sensitivity to the range. This is more honest and more useful than claiming precision on a point that requires professional tax judgment.
This article is for educational purposes only. It explains valuation concepts and modeling choices. It is not investment advice, a recommendation, or a financial promotion. Examples use illustrative inputs. Verify all data using primary sources and consult an appropriately licensed professional before making financial decisions.
CFA® and Chartered Financial Analyst® are registered trademarks owned by CFA Institute. This content is not endorsed by or affiliated with CFA Institute.
Abdul Gaffar Mohammed, CFA
Treasury & Investment Professional