Currency Hedging: How FX Changes Portfolio Returns

Currency risk can change a good investment return

Buying an overseas asset creates two moving parts for a UK investor: the asset's return in its local currency and the change in that currency against sterling. A share can rise in dollars while the investor earns much less in pounds if the dollar weakens.

Learning objective: calculate an overseas investment's home-currency return, distinguish hedged and unhedged exposure, and choose a deliberate currency policy rather than accepting one by accident.

বাংলায় পড়ুন: Currency Hedging: FX Move Portfolio Return কীভাবে বদলায়

The FCA requires relevant investment disclosures to explain that returns on investments denominated outside sterling are exposed to exchange-rate risk. This risk can help or hurt; it is not automatically a reason to hedge.

1. Calculate the combined return correctly

For a UK investor, an approximate sterling return is:

(1 + local asset return) × (1 + currency return against GBP) − 1

The currency return is positive when the foreign currency strengthens against sterling and negative when it weakens.

Worked example

Assume a UK investor buys a US equity fund:

• the fund rises 8% in US dollars;
• the dollar falls 5% against sterling;
• fees and tax are ignored.

The sterling return is:

(1.08 × 0.95) − 1 = 2.6%

Adding 8% and −5% gives 3%, which is close but not exact because returns compound. If the dollar had risen 5%, the sterling return would have been 13.4%: (1.08 × 1.05) − 1.

2. Trading currency is not always the underlying exposure

The exchange on which a fund trades and the currency displayed on the screen do not necessarily determine its economic currency exposure. A global equity ETF quoted in pounds can still own US, European and Japanese companies. Paying in sterling removes the conversion step at purchase; it does not automatically hedge the underlying currencies.

Check the fund's factsheet for:

• portfolio currency exposures;
• whether the share class is explicitly currency hedged;
• the currency to which it is hedged;
• hedge frequency and benchmark methodology;
• ongoing charges, transaction costs and tracking difference.

3. What a hedged share class does

A currency-hedged fund commonly uses rolling forward contracts or similar derivatives to offset much of the portfolio's foreign-currency movement against a chosen base currency. For example, a GBP-hedged global equity fund seeks to reduce the effect of foreign currencies moving against sterling.

Hedging reduces currency variation; it does not remove investment risk. The hedge can be imperfect because portfolio values move between rebalancing dates, costs and interest-rate differences affect returns, and the hedge may not cover every exposure. A current iShares GBP-hedged world fund description says its currency exposure is hedged monthly and explicitly notes that hedging is designed to reduce, but cannot eliminate, currency effects (fund information).

4. When hedging may be useful

Hedging can be more valuable when:

1. the investment funds a known sterling liability on a defined date;
2. currency swings would dominate the expected asset return;
3. the asset is intended to stabilise the portfolio, as with high-quality bonds;
4. the investor cannot tolerate a large FX-driven drawdown;
5. the strategy has a short horizon and little time for currency moves to reverse.

For bonds, expected returns are often lower than for equities, so FX volatility can overwhelm the stabilising role. Vanguard's research argues that hedging global fixed income back to the home currency can preserve that role (research summary).

5. When remaining unhedged may be reasonable

An investor may accept unhedged exposure when:

• the horizon is long and foreign currency diversifies sterling risk;
• future spending will occur in the same foreign currency;
• the hedge cost or product complexity is unattractive;
• the portfolio intentionally holds foreign currencies as a shock absorber;
• the investor understands that FX can magnify both gains and losses.

An unhedged holding is still an active risk decision. Write down why the exposure belongs in the portfolio and what would cause the policy to change.

6. Company exposure is more complex than listing currency

A UK-listed company can earn most of its revenue abroad, while a US-listed company can have large sterling or euro costs. Translation exposure affects reported earnings; transaction exposure affects cash flows; economic exposure affects long-term competitiveness.

Therefore, hedging the currency of a stock-market listing does not perfectly hedge the company's business exposure. Read revenue geography, cost geography and company hedging disclosures before assuming a simple one-currency relationship.

7. Partial hedging and matching liabilities

The choice does not have to be 0% or 100%. An investor can hedge only the portion linked to near-term sterling needs and leave long-term growth assets unhedged. Another practical approach is to match assets to liabilities: sterling assets for sterling spending, and foreign-currency assets for known overseas costs.

Review the hedge on a schedule rather than reacting to every currency move. Chasing the currency after a large move can lock in losses and turn risk management into short-term speculation.

Common mistakes

1. Assuming a GBP trading line is GBP hedged. Quote currency and economic exposure are different.
2. Adding asset and FX returns. The exact combined result is multiplicative.
3. Ignoring hedge costs and tracking difference. A hedge has implementation effects.
4. Hedging the wrong currency. Company revenues and fund holdings may differ from listing currency.
5. Changing policy after every FX move. That is market timing, not a stable risk process.
6. Using leveraged FX products as a casual hedge. Margin calls and rollover risk can create a larger problem.

Practical checklist

• Define the portfolio's home currency and future spending currency.
• List each holding's underlying currency exposure.
• Confirm whether each share class is hedged or unhedged.
• Calculate returns using the compounded formula.
• Compare fees, hedge methodology and tracking difference.
• Stress a 5%, 10% and 15% adverse currency move.
• Match near-term liabilities with suitable currency assets.
• Set a target hedge ratio and review schedule.
• Record why the policy fits the portfolio's horizon and risk tolerance.

Key takeaway

Currency hedging is a portfolio-design choice, not a forecast that one currency will rise or fall. Start with the investor's liabilities and time horizon, identify the true economic exposure, quantify how FX changes returns, and use a consistent hedge policy that accounts for cost and imperfection.

Educational information only. This is not personalised investment advice or a recommendation to buy, sell or hedge any asset. Currency movements, derivatives and investments can cause losses. Check current product documents and seek regulated advice where appropriate.