How crypto swaps reset Portugal's 365-day tax exemption (and the one exception).

Tax is only triggered when crypto is converted to fiat. The 365-day exemption is a separate doctrine. The two are constantly conflated, and getting them wrong is expensive.

If you traded crypto in Portugal in 2025, the single most common mistake I see in declarations is a confusion between two rules. They sound related. They are actually independent, and conflating them has cost Portuguese taxpayers real money.

This piece walks through both rules, shows two worked examples where the confusion costs the exemption, and lays out the narrow case where the original holding period survives a swap.

Doctrine one: when does tax happen.

The rule is statutory, not administrative. Article 10, paragraph 20, of the IRS Code defers taxation in a crypto-for-crypto disposal until the moment the consideration is no longer a crypto-asset. The swap itself is not a taxable event; the taxable moment is the conversion to fiat.

A BTC-for-ETH swap triggers nothing. An ETH-for-USDT swap triggers nothing. Tax only arrives when you sell to euros. Article 10(21) carves this out where the counterpart is not resident in another EU/EEA Member State or in a jurisdiction with a tax treaty or information-exchange agreement with Portugal.

Doctrine two: when does the 365-day clock run.

Portugal's famous long-term crypto exemption lives in Article 10(19) of the IRS Code (CIRS): gains on crypto-assets held uninterruptedly for 365 days or more are not taxed.

The question is what counts as the holding period when a swap has happened along the way. Under a strict reading of Article 10(20), the swap is a disposal: the clock for the original asset stops at the swap, and a new clock for the new asset starts at the swap. The two ideas, untaxed swap and reset clock, coexist.

Two worked examples.

The narrow exception: PIV 28969.

In October 2025, the PTA published a second binding information, No. 28969, which carved out one situation where the clock is preserved through a swap. This is the so-called "technical conversion" exception, in its narrow sense.

The factual matrix the PTA addressed combined these elements.

• One uninterrupted swap-then-sell sequence. The swap to the stablecoin and the sale to euros must be executed as a single, continuous transactional sequence. The PIV uses "imediato" (immediate); the AT reads it as an uninterrupted sequence with no economic exposure between the two legs. Holding the stablecoin for hours, let alone days, exposes the taxpayer to a clock reset because the stablecoin becomes a standalone position rather than a transit step.
• Swap justified by absence of a direct EUR pair. In the PIV's facts, the source asset had no liquid direct EUR market on the exchange used, which justified routing through a stablecoin. The PTA frames this as part of why the swap is technical rather than economic, not as a formal condition of the rule.
• Counterpart inside the EU/EEA/treaty perimeter (Art. 10(21) CIRS). The statutory carve-out from swap-neutrality applies whenever the counterpart is not resident in another EU/EEA Member State or in a jurisdiction with a tax treaty or information-exchange agreement with Portugal. If your counterpart sits outside that perimeter, neither the swap-neutrality nor PIV 28969's preservation of the clock is available.

When the situation matches, the gain on the eventual EUR sale is calculated against the original acquisition cost of the source asset, and the holding period is the original holding period. The swap is treated as a technical step rather than an economic event.

A caveat worth knowing. A binding information binds the tax authority only as to the taxpayer who requested it. Other taxpayers cannot rely on it as if it were law. Some legal firms have publicly criticised the technical-conversion doctrine as legally weak and lacking a clear statutory anchor. Treat PIV 28969 as guidance on how the PTA is currently reasoning, not as a safe harbour.

The decision table.

Five common scenarios. The first column is what happened. The second is whether the 365-day clock resets. The third is the tax outcome on a final sale to euros.

What this means in practice.

Three practical implications, in order of importance.

• If you want the 365-day exemption, hold the original asset uninterrupted. The cleanest path to 0% is the path with no swaps. Plan around this.
• If you must rotate, mind the perimeter and the timing. The statutory swap-neutrality of Article 10(20), and the technical-conversion preservation of the clock under PIV 28969, only hold when the counterpart sits in the EU/EEA/treaty perimeter (Article 10(21)) and the swap-then-fiat-sale is genuinely immediate. Keep evidence of original acquisition, exchange selection, counterpart jurisdiction, and timing. Without it, neither rule protects you.
• Map your swap history before you file. Every disposal in your records changes the maths; every undocumented one creates risk. The 365-day rule is binary in result and forensic in proof. Map first, file second.

More questions answered in the dedicated FAQ section: Topic 02 - Crypto and the 365-day rule.