Buying a Ruin to Rebuild Will Not Shelter Your Home-Sale Gains From IRS, the Tax Authority Rules
The Tax and Customs Authority has ruled that buying a property classified as a ruin does not count as reinvestment for the IRS capital-gains exemption, because a ruin cannot be a permanent home at the moment of purchase. Here is what the rule requires — and how to avoid the trap.
Buying a derelict house to rebuild as your dream home is one of the most common expat projects in Portugal — and the tax authority has just made clear it will not shield the proceeds of a previous home sale. In a binding ruling published this week, the Autoridade Tributária e Aduaneira (Tax and Customs Authority, or AT) held that purchasing a property classified as a ruin does not count as reinvestment for the purposes of the capital-gains exemption in personal income tax (IRS).
The decision (reference PIV_25960) answers a specific taxpayer's question. Having sold their permanent home in October 2023 and used part of the proceeds to pay off the mortgage, the taxpayer wanted to reinvest the rest in an urban property registered as a ruin, rebuild it, and make it their new permanent residence. The AT's answer was blunt: a ruin "will not, for obvious reasons, have the capacity to be considered a primary and permanent residence and tax domicile" at the moment it is bought — so the purchase does not qualify.
What the exemption actually requires
Under Article 10 of the IRS Code, gains from selling a permanent home escape tax if the money is reinvested in another permanent home, in building land, or in the construction, expansion or improvement of a property used exclusively for the same purpose. The rules are tightly timed: the reinvestment must fall within the window running from 24 months before the sale to 36 months after it; any mortgage on the old home must be repaid within three months; the seller must declare the intention to reinvest in the IRS return for the year of the sale; and the new property must actually be occupied as the household's permanent residence and tax domicile within 12 months, or the break is lost.
The trap is the wording "another permanent home." A ruin, by definition, cannot be lived in on the day of purchase, so the AT treats the acquisition itself as falling outside the exemption — regardless of the buyer's genuine intention to rebuild. Crucially, the taxpayer had also proposed excluding the reconstruction costs from the reinvestment calculation, which left only the bare purchase of an uninhabitable shell to test the rule.
What This Means for Expats
- Buy land, not a ruin, if you can. The exemption explicitly covers "a terreno para construção" (building land) and construction on it. A plot bought for building is treated more favourably than a structure the tax office deems uninhabitable.
- Sequence the money carefully. If your plan is sale-then-rebuild, the safer route may be to reinvest in improving or extending a home you can already occupy, rather than sinking the gain into a shell that only becomes a home later.
- Mind the clock. The three-month mortgage-repayment rule and the 12-month occupancy deadline are unforgiving; a slow renovation or a delayed habitation licence can retroactively cost you the exemption.
- Get a binding ruling of your own. Because these outcomes turn on fine facts, a pedido de informação vinculativa to the AT before you commit can lock in certainty rather than gambling on a filing.
The ruling fits a pattern of the AT reading Article 10 narrowly — it has recently refused to extend reinvestment deadlines for licensing delays and limited the exemption for buyers purchasing jointly. For readers weighing the property-tax picture, see our practical guide to paying IMI in 2026, the new ten-year Treasury certificate, and how the state clawed back a record €1.55 billion in enforced tax collection.
