S&P 500 Index Fund: Best Funds, Returns, Tax Guide for Ireland

Few financial products spark as much debate—and deliver as consistently—as the S&P 500 index fund. For Irish investors, the choice goes beyond picking the cheapest fund: tax rules, dividend withholding, and deemed disposal all shape the real return. This guide breaks down the best funds, the tax reality, and whether you should put your money in at all.

S&P 500 10-year annualized return (as of 2024): ~12.1% ·
Average dividend yield: 1.3% ·
Lowest expense ratio among S&P 500 index funds: 0.015% (Fidelity FXAIX) ·
Warren Buffett’s recommended allocation for most investors: 90% S&P 500 index fund, 10% short-term bonds ·
Number of companies in S&P 500: 500

Here are the key specifications of the S&P 500 index and its leading funds:

Which is the best S&P 500 fund?

Warren Buffett’s recommended S&P 500 fund

• Warren Buffett has repeatedly argued that most investors are better off in a very low-cost broad index fund rather than active stock picking (YouTube interview clip).
• He has specifically recommended low-cost S&P 500 index funds in public remarks over the years (YouTube interview clip).
• His 2013 letter to Berkshire Hathaway shareholders states: “The best way to own common stocks is through an index fund that charges very low fees.”

The implication: Buffett’s advice points to a fund that tracks the S&P 500 with an expense ratio below 0.10%. Vanguard S&P 500 ETF (VOO) at 0.03% and Fidelity 500 Index Fund (FXAIX) at 0.015% both fit the bill—but neither is UCITS-compliant, which matters for European buyers.

Comparing Vanguard, Fidelity, and UBS S&P 500 index funds

Three leading funds, one clear trade-off: cost versus accessibility across borders.

The pattern: Irish residents face a higher total cost if they buy US-listed ETFs—30% US dividend withholding versus 15% with a UCITS wrapper (ETF.ie comparison). The lower expense ratio of a US fund can be wiped out by the withholding gap.

Key metrics: expense ratio, tracking error, assets under management

• Expense ratio: The cheapest option is Fidelity FXAIX at 0.015% (Bogleheads wiki).
• Tracking error: Most major S&P 500 index funds track within 0.01–0.05% of the index annually.
• Assets under management: VOO has over $1 trillion AUM; IVV has over $500 billion; CSPX has approximately $50 billion and growing.
• For Irish investors, a UCITS fund with a slightly higher expense ratio may still win after tax — the difference in dividend withholding alone is ~15 basis points per year.

What is 10 year return on S&P 500?

Hypothetical: $1,000 invested 10 years ago

• S&P 500 10-year annualized return is approximately 12% as of 2024.
• A $1,000 investment 10 years ago would be worth roughly $3,100 with reinvested dividends.
• Returns vary based on reinvestment of dividends and market cycle — the nominal growth is 210%, but the real return after Irish inflation and tax is lower.
• That same $1,000, if held in a US-listed ETF by an Irish resident, would face 30% US dividend withholding on dividends plus deemed disposal at 38% on gains — significantly reducing the net figure.

The catch: the headline 12% annualized return is a gross figure. For an Irish investor in a US-listed ETF, the effective after-tax return could be closer to 7–8% after accounting for dividend withholding, exit tax, and currency effects.

Annualized returns vs cumulative returns

• Annualized return (CAGR) smooths volatility into a single yearly rate. The 10-year CAGR for the S&P 500 is ~12.1% as of December 2024.
• Cumulative return over the same period is roughly 210% — but this masks the 2020 COVID crash and subsequent recovery.
• Irish investors need to consider that deemed disposal applies every 8 years, meaning gains are crystallized for tax purposes regardless of whether the investor sells.

Factors influencing S&P 500 performance over the decade

• Technology sector dominance: Apple, Microsoft, Nvidia, and Alphabet now represent over 20% of the index. This concentration drives returns but also increases sector risk.
• Low interest rates from 2013–2021 fueled multiple expansion; rising rates in 2022–2023 compressed valuations.
• Buyback activity: S&P 500 companies spent over $800 billion on share buybacks in 2023 alone, mechanically boosting EPS growth.
• Currency impact for non-US investors: USD appreciation against the euro added roughly 2–3% annualized to returns for European holders over the decade.

Can I invest in the S&P 500 from Ireland?

Tax implications: deemed disposal and ETF reporting for Irish residents

• Irish-resident investors in ETFs are generally subject to a special fund tax regime rather than capital gains tax (Oireachtas answer on tax code).
• Revenue states that Irish-domiciled ETFs and EU-domiciled ETFs are treated under the same investment undertaking rules (Revenue ETF tax guidance).
• Irish ETF tax treatment includes a deemed disposal after 8 years (CloudAccounts guide).
• Irish ETF exit tax was reduced from 41% to 38% from 1 January 2026 for Irish and EU/EEA-domiciled ETFs (Fairstone Ireland).
• Older Irish media guidance described Irish-domiciled ETFs as typically subject to 41% exit tax (The Irish Times).

What this means: an Irish investor holding a UCITS S&P 500 ETF for 10 years would pay 38% exit tax on gains accumulated in the first 8 years, then ongoing deemed disposal every 8 years after that. This is worse than the 33% CGT rate on direct shareholding — but there is no CGT on individual US stocks held by Irish residents unless they are considered “offshore funds.”

Broker options for Irish investors

• Irish residents can invest through brokers like Degiro, Interactive Brokers, and Irish-based platforms.
• A self-assessed Irish investor may need to file Form 11, while smaller dividend amounts can be reported through Form 12 in some cases (CloudAccounts guide).
• If foreign tax is withheld on dividends, an Irish investor may be able to claim a foreign tax credit subject to treaty rules (CloudAccounts guide).
• Irish-domiciled UCITS ETFs can receive US dividends with 15% withholding under the Ireland–US treaty (ETF.ie comparison).
• US-listed S&P 500 ETFs face 30% withholding on US dividends (ETF.ie comparison).

S&P 500 ETFs available in Ireland (iShares, Vanguard, UBS)

• iShares Core S&P 500 UCITS ETF (CSPX): 0.07% TER, accumulating, IE-domiciled, UCITS compliant — the most straightforward option for Irish investors.
• Vanguard S&P 500 UCITS ETF (VUSA): 0.07% TER, distributing, IE-domiciled — pays dividends, which are taxable as income.
• UBS S&P 500 Index Fund: ~0.09% TER, UCITS compliant mutual fund structure — available on some Irish platforms.
• A 2026 Irish investing guide states that Ireland-domiciled ETFs can be a tax-efficient wrapper for Irish investors compared with directly buying US-listed ETFs (Fairstone Ireland).
• Irish funds are generally exempt from Irish tax on income and gains derived from their underlying investments (ETF Ireland Guide 2025).

Should I put all my money in the S&P 500?

Risks of concentrated investing in US large caps

• S&P 500 is not risk-free; it concentrates in US large-cap growth stocks. The top 10 holdings represent roughly 30% of the index.
• Warren Buffett recommends 90% in a low-cost S&P 500 index fund and 10% in short-term government bonds, not 100% (YouTube interview clip).
• If US large caps underperform for a decade (as they did in 2000–2009), a 100% S&P 500 portfolio would have delivered negative real returns.

Diversification benefits across asset classes

• Adding international stocks (e.g., a global ex-US index) reduces volatility without materially reducing long-term returns.
• Adding bonds provides a buffer during equity drawdowns — the Buffett 90/10 split suggests 10% in short-term government bonds.
• For Irish investors, holding property or REITs through Irish tax wrappers may provide additional diversification with different tax treatment.

Alternatives to putting all money in the S&P 500

• Global equity index fund: MSCI World or FTSE All-World covers US + developed + emerging markets.
• Bond allocation: Irish government bonds or EU government bond ETFs for capital preservation.
• Managed funds: Some Irish-domiciled funds are taxed under different rules — but always check the tax classification first.
• Direct stock holdings: Individual US stocks held by Irish residents are taxed at 33% CGT, not the 38% ETF exit tax — but you lose index diversification.

How should a beginner invest in the S&P 500?

Step-by-step: open a brokerage account, choose a fund, start investing

1. Step 1: Open a brokerage account — Degiro, Interactive Brokers, or Trading 212 all offer access to UCITS ETFs for Irish residents.
2. Step 2: Choose a fund — iShares Core S&P 500 UCITS ETF (CSPX, accumulating) or Vanguard S&P 500 UCITS ETF (VUSA, distributing).
3. Step 3: Fund your account and place your first buy order — most brokers allow fractional shares on ETFs.
4. Step 4: Set up recurring contributions — monthly or quarterly investments via dollar-cost averaging.
5. Step 5: Reinvest dividends (if using a distributing fund) or hold an accumulating fund that does it automatically.

Minimizing costs: expense ratios, commissions, and tax efficiency

• Expense ratio: Target 0.07% or less for UCITS S&P 500 ETFs.
• Commissions: Degiro offers a core selection of ETFs with zero commission on one buy/sell per month; Interactive Brokers charges ~€1–3 per trade.
• Tax efficiency: Use an accumulating UCITS ETF to avoid dividend distribution tax and the need to reinvest manually. CSPX (0.07%) is the most popular choice.
• Spread costs: CSPX has a typical bid-ask spread of 0.01–0.05% on major exchanges like Xetra or LSE.

Long-term strategy: dollar-cost averaging and staying invested

• Dollar-cost averaging (regular fixed contributions) reduces the risk of investing a lump sum at a market peak.
• Historically, lump sum investing outperforms DCA ~65% of the time over 10-year horizons, but DCA reduces regret risk for beginners.
• For Irish investors, make sure your ETF is classified correctly for tax: Revenue’s guidance confirms that UCITS ETFs are treated under the investment undertaking regime (Revenue ETF tax guidance).
• The key long-term lever is not fund selection — it is staying invested through bear markets and continuing contributions.

For a broader overview of how these funds work, you might find this S&P 500 index funds guide helpful.

Frequently asked questions