ETF vs index fund: differences, taxation and which to choose in Spain

An ETF (exchange-traded fund) and a traditional index fund chase the same goal: tracking an index like the S&P 500 or the MSCI World at the lowest possible cost. The investing logic is identical; what changes is how you buy them and, above all, how they are taxed in Spain.

How you buy them

• ETF: trades on an exchange like a stock. You buy and sell it in real time through a broker, with its own bid/ask spread and, with many brokers, a per-trade commission.
• Index fund: subscribed and redeemed at a single daily price (NAV), usually with no buy/sell commission, through a platform or fund manager.

The big difference: taxation in Spain

This is the key point that usually decides it for a Spanish resident retail investor: investment funds let you switch between funds without being taxed (see our article on index fund taxation), while selling an ETF to buy another one does trigger a capital gain subject to income tax at the moment of sale.

If your strategy is "buy and hold" for decades without touching it, this matters less. If you expect to rebalance, change provider, or adjust your portfolio over time, the index fund lets you do so without paying tax upfront.

Fees: increasingly similar

Years ago ETFs had lower TERs than equivalent index funds; today the gap has narrowed a lot, and there are index funds with TERs as low as many ETFs in the same category. Always compare the actual TER of each specific product, not a general rule.

Other differences worth knowing

• Small periodic contributions: funds let you subscribe exact amounts (e.g. €100) without worrying about the price of a whole share or broker commissions; with an ETF you depend on whether your broker allows fractional purchases.
• Accumulating vs distributing: both ETFs and funds exist in both variants (see our glossary); it is not a criterion that tells them apart.
• Availability: some very specific indices or niches are only available as an ETF.

In short

• Same investing philosophy (tracking an index at low cost); different legal and tax wrapper.
• In Spain, index funds usually win thanks to tax-free switching, unless you need an index that only exists as an ETF.
• Always compare the actual TER of each specific product before deciding.