Exchange Rate Assumptions in DCF Models: Translating Multi-Currency Cash Flows

The HKMA’s 2024 annual report, published in April 2025, confirmed that Hong Kong’s external portfolio liabilities reached HKD 13.4 trillion, with a significant portion denominated in USD and RMB. For CFOs of Hong Kong-listed companies with cross-border operations, this is not merely a macro statistic—it represents the scale of currency exposure embedded in their cash flow projections. The shift in the USD/CNH exchange rate from 7.12 in January 2024 to 7.27 in December 2024, a 2.1% depreciation of the renminbi, erased an estimated HKD 281 billion in translated revenue for Hang Seng Index constituents with mainland operations, according to Bloomberg consensus data. Standard DCF models that assume a static exchange rate or a simple linear projection are no longer defensible in board presentations. The SFC’s 2023 consultation on the Code of Conduct for sponsors explicitly flagged currency risk disclosure as a recurring deficiency in listing documents, and the HKEX’s 2024 guidance note on financial forecasts (HKEX-GL112-24) now requires issuers to stress-test multi-currency assumptions. This article provides a technical framework for translating multi-currency cash flows in DCF models, anchored in Hong Kong’s regulatory expectations and observable market mechanics.

The Fallacy of the Single-Currency DCF in a Multi-Currency Reality

The most common error in cross-border DCF analysis is the assumption that a single functional currency can capture the economic substance of a business with operations in multiple jurisdictions. Under HKAS 21 (The Effects of Changes in Foreign Exchange Rates), a Hong Kong-listed company must determine its functional currency based on the primary economic environment in which it operates. For a company incorporated in Bermuda with a Cayman Islands holding structure, a Hong Kong listing, and mainland China operating subsidiaries, the functional currency is rarely HKD—it is typically RMB for the operating entities and USD or HKD for the reporting entity.

The translation process introduces three distinct sources of volatility: transaction exposure from individual cash flows, translation exposure from consolidating subsidiary financials, and economic exposure from competitive dynamics. A DCF model that uses a single exchange rate to translate all future RMB cash flows into HKD at the terminal value stage is mathematically equivalent to assuming zero volatility in the exchange rate—an assumption that failed spectacularly for property developers in 2022-2023. The Hang Seng Mainland Properties Index fell 47% in 2022, but the underlying RMB-denominated cash flows of developers like Country Garden and Shimao were already deteriorating faster than the HKD translation could capture.

The Nominal Versus Real Exchange Rate Trap

Practitioners frequently conflate nominal exchange rates with real exchange rates when projecting long-term cash flows. The nominal exchange rate reflects the relative price of two currencies, while the real exchange rate adjusts for inflation differentials. For a DCF model with a 10-year projection period, the difference is material. If the annual inflation differential between Hong Kong (2.0% CPI in 2024) and mainland China (0.2% CPI in 2024) persists, the real exchange rate implies a gradual appreciation of the RMB against the HKD in purchasing power terms, even if the nominal rate depreciates.

The correct approach is to project cash flows in the currency of the operating entity (typically RMB for mainland operations), discount them at the cost of capital appropriate to that currency, and then translate the resulting present value at the spot exchange rate. This is the “forward parity” method endorsed by the CFA Institute curriculum. Applying a Hong Kong WACC of 8.5% to RMB cash flows and then translating at a projected future exchange rate double-counts the currency risk—once in the discount rate and once in the translation rate.

Regulatory Scrutiny Under HKEX-GL112-24

The HKEX’s guidance note on financial forecasts, issued in December 2024, explicitly requires issuers to disclose the exchange rate assumptions used in any projected financial information included in listing documents or circulars. Paragraph 4.7 of HKEX-GL112-24 states that “where the forecast involves translation of cash flows from a foreign currency, the issuer must provide a sensitivity analysis showing the impact of a +/- 5% change in the exchange rate on the forecast results.”

This is not a suggestion—it is a listing requirement for any document that includes profit forecasts or financial projections. For sponsors preparing a prospectus under the SFC’s Code of Conduct (paragraph 17.6), the failure to stress-test exchange rate assumptions can constitute a breach of the duty to exercise due diligence. In the 2023 SFC enforcement action against a sponsor for the listing of a mainland pharmaceutical company, one of the cited deficiencies was the use of a single exchange rate assumption for five years of projected cash flows without any sensitivity analysis.

Constructing the Multi-Currency Cash Flow Waterfall

The correct structure for a multi-currency DCF is a “waterfall” that traces cash flows from the operating subsidiary through the holding structure to the ultimate shareholder. For a typical Hong Kong-listed company with a BVI intermediate holding company and a Cayman Islands parent, the cash flow path involves three currency transitions: from the operating currency (RMB) to the intermediate currency (USD) via dividend repatriation, and from the intermediate currency to the reporting currency (HKD) via the listed entity’s financial statements.

Each transition introduces a different exchange rate regime. The RMB-to-USD conversion is subject to PRC foreign exchange controls under the State Administration of Foreign Exchange (SAFE) regulations, which impose a cap on dividend repatriation equivalent to the subsidiary’s distributable profits as verified by a PRC auditor. The USD-to-HKD conversion is a free-market transaction under Hong Kong’s linked exchange rate system, but the effective rate depends on the timing of the conversion and the size of the transaction relative to market liquidity.

Step 1: Project Operating Cash Flows in Local Currency

The operating cash flows of a mainland subsidiary must be projected in RMB, using inflation assumptions consistent with the PRC economic environment. The PRC’s GDP deflator was -0.1% in 2024, reflecting deflationary pressures in the industrial sector, while the services sector CPI was 1.2%. A DCF model that uses a single inflation rate for all components of the cash flow is mis-specified. Revenue growth should be projected using industry-specific price indices, while cost growth should use the producer price index (PPI), which was -2.3% year-on-year in December 2024.

The discount rate for these RMB cash flows should be a RMB-denominated WACC, derived from the PRC risk-free rate (the 10-year PRC government bond yield, which was 2.1% in January 2025) plus an equity risk premium appropriate to the industry. Applying a Hong Kong risk-free rate of 3.8% (based on the 10-year HKD government bond yield) to RMB cash flows would overstate the cost of capital by 170 basis points, inflating the discount rate and understating the present value.

Step 2: Apply the Dividend Repatriation Constraint

Not all operating cash flows are distributable. Under PRC company law, a wholly foreign-owned enterprise (WFOE) can only distribute dividends from accumulated profits as verified by a PRC-certified public accountant. The maximum distributable amount is the lower of the subsidiary’s retained earnings and its cash balance, after deducting statutory reserves (10% of after-tax profits until the reserve reaches 50% of registered capital).

For a DCF model, the relevant cash flow is not the operating cash flow of the subsidiary but the dividend that can be legally repatriated to the BVI holding company. This dividend is subject to a 5% withholding tax under the PRC-Hong Kong Double Tax Arrangement, provided the Hong Kong parent is the beneficial owner and meets the substance requirements under the Arrangement. If the parent is a BVI company without Hong Kong tax residence, the withholding tax rate increases to 10%.

The timing of dividend repatriation is also constrained. SAFE requires that dividends be paid within six months of the shareholder resolution, and the exchange rate used for the conversion is the spot rate on the date of the actual remittance, not the date of the resolution. A DCF model that assumes immediate repatriation at a projected exchange rate is ignoring a 6-month lag that can introduce significant timing risk.

Step 3: Translate at the Forward Rate, Not the Spot Rate

The correct exchange rate for translating future dividends from USD to HKD is the forward rate implied by the interest rate differential between the two currencies, not the spot rate. Under covered interest rate parity, the forward rate is determined by the spot rate adjusted for the difference between the USD and HKD interest rates. As of January 2025, the 1-year USD/HKD forward rate was 7.82, compared to the spot rate of 7.77, reflecting the 50-basis-point premium of HKD interest rates over USD interest rates.

Using the spot rate to translate a dividend expected in 12 months would understate the HKD value by 0.64%. While this may appear immaterial for a single year, the compounding effect over a 10-year projection period is significant. If the interest rate differential persists, the cumulative understatement reaches 6.6% by year 10. For a company with HKD 1 billion in annual dividends, this translates to a HKD 66 million error in the terminal value calculation.

The Terminal Value Conundrum in Multi-Currency Models

The terminal value typically represents 60-80% of the total enterprise value in a DCF model, making the exchange rate assumption for the terminal year the single most consequential input. The standard Gordon Growth Model formula—terminal value = FCF * (1+g) / (WACC - g)—assumes a perpetual growth rate in the currency of the cash flows. When the cash flows are in RMB and the terminal value is translated to HKD, the growth rate must be consistent with the long-run equilibrium exchange rate.

The Purchasing Power Parity Anchor

The long-run equilibrium exchange rate between the RMB and the HKD is anchored by purchasing power parity (PPP), which predicts that exchange rates will adjust to equalize the price levels of a basket of goods across countries. The IMF’s 2024 estimate of the RMB’s PPP exchange rate against the USD was 4.2 RMB per USD, compared to the market rate of 7.27. This implies that the RMB is undervalued by approximately 42% on a PPP basis.

For a terminal value calculation, the implication is that the RMB should appreciate against the USD (and by extension against the HKD, which is pegged to the USD) over the long term. A DCF model that assumes a constant nominal exchange rate in perpetuity is implicitly assuming that the RMB remains 42% undervalued forever—an assumption that contradicts the fundamental economic forces that drive exchange rates toward PPP over multi-decade horizons.

The Uncovered Interest Rate Parity Adjustment

A more defensible approach is to use uncovered interest rate parity (UIP), which posits that the expected change in the exchange rate equals the interest rate differential between the two currencies. Under UIP, the expected annual depreciation of the HKD against the RMB equals the difference between the HKD interest rate and the RMB interest rate. As of January 2025, the 1-year HKD LIBOR was 4.8%, while the 1-year PRC government bond yield was 1.9%, implying an expected annual depreciation of the RMB of 2.9% relative to the HKD.

Incorporating UIP into the terminal value requires adjusting the growth rate in the Gordon Growth Model to reflect the expected exchange rate change. If the terminal growth rate in RMB is 3.0% and the expected annual RMB depreciation is 2.9%, the effective growth rate in HKD terms is 0.1%. This adjustment reduces the terminal value dramatically—for a company with HKD 1 billion in terminal year free cash flow, the terminal value drops from HKD 20.0 billion (using 3.0% growth and 8.0% WACC) to HKD 12.7 billion (using 0.1% effective growth), a reduction of 36.5%.

The SFC’s Preference for Scenario Analysis

The SFC’s 2023 thematic review of valuation practices in takeovers and privatizations (published in February 2024) found that 78% of valuation reports relied on a single terminal value assumption without any scenario analysis. The review specifically criticized the use of perpetuity growth rates that were inconsistent with the macroeconomic environment of the currency in which the cash flows were denominated.

For a Hong Kong-listed company with mainland operations, the SFC expects at least three scenarios for the terminal value: a base case using UIP-consistent exchange rate assumptions, a bull case assuming convergence to PPP over 10 years, and a bear case assuming the current undervaluation persists. Each scenario must be presented with a clear rationale and a sensitivity table showing the impact on the valuation range.

Practical Implementation for CFOs and Advisors

The technical framework described above must be translated into a workable model that can withstand regulatory scrutiny and board-level challenge. The following implementation steps are designed to align with the HKEX’s disclosure requirements and the SFC’s expectations for sponsor due diligence.

Model Architecture and Documentation

The DCF model should be structured as a set of linked workbooks, with one workbook per operating currency. Each currency-specific workbook contains the projected cash flows, the inflation assumptions, and the discount rate appropriate to that currency. A master workbook performs the translation using a separate exchange rate assumption sheet that contains the forward rates, the PPP estimates, and the UIP-implied rates for each projection year.

All exchange rate assumptions must be sourced from observable market data. The HKEX’s guidance note requires that “any exchange rate assumption used in a forecast must be based on a published source that is readily verifiable.” Acceptable sources include the HKMA’s daily exchange rate statistics, Bloomberg’s forward rate curves, and the IMF’s International Financial Statistics database. Internal estimates or management forecasts are not acceptable without a detailed justification and sensitivity analysis.

Sensitivity and Stress Testing

The minimum disclosure required under HKEX-GL112-24 is a sensitivity analysis showing the impact of a +/- 5% change in the exchange rate on the valuation. However, the SFC’s 2024 consultation on financial forecasts suggests that this minimum is insufficient for companies with material currency exposure. The consultation paper proposes that issuers should also show the impact of a 2-standard-deviation move in the exchange rate based on the historical volatility of the currency pair.

For the USD/CNH pair, the 5-year annualized volatility was 4.8% as of December 2024, implying a 2-standard-deviation move of 9.6%. A stress test at this level would show the impact of the RMB moving to 7.96 against the USD (a 9.6% depreciation) or to 6.58 (a 9.6% appreciation). For a company with HKD 5 billion in translated revenue, the difference between these two scenarios is HKD 960 million.

Board and Audit Committee Reporting

The audit committee of a Hong Kong-listed company has a specific responsibility under the HKEX’s Corporate Governance Code (Code Provision D.2.1) to review the company’s financial reporting and the effectiveness of its internal controls. Exchange rate assumptions in DCF models used for impairment testing, acquisition valuation, or strategic planning must be reviewed by the audit committee as part of the financial reporting process.

The board should receive a memorandum that summarizes the exchange rate assumptions, the sources of those assumptions, and the results of the sensitivity analysis. The memorandum should also include a comparison of the assumptions used in the current period against those used in the prior period, with an explanation of any changes. This documentation is critical for defending the valuation in the event of a regulatory inquiry or a shareholder challenge.

Actionable Takeaways

1. Structure all multi-currency DCF models using the “waterfall” approach—project operating cash flows in the local currency, apply legal and regulatory repatriation constraints, and translate at forward rates rather than spot rates.
2. Disclose all exchange rate assumptions with verifiable market sources in compliance with HKEX-GL112-24, and include a sensitivity analysis showing the impact of a +/- 5% change as a minimum.
3. Adjust the terminal value growth rate for the expected exchange rate change under uncovered interest rate parity, and present at least three scenarios (base, bull, bear) to satisfy SFC expectations from the 2023 thematic review.
4. Ensure the audit committee reviews exchange rate assumptions used in impairment testing and strategic valuations, with documentation comparing current and prior period assumptions.
5. For any dividend repatriation from PRC subsidiaries, model the 6-month SAFE remittance lag and the applicable withholding tax rate under the PRC-Hong Kong Double Tax Arrangement, not the statutory rate.