A Mortgage When One Contributes More: Percentages and Ownership

The land registry extract isn't the truth, it's just what's on paper

There's a conversation that recurs in many Spanish couples at the most inopportune moment: three weeks before signing the mortgage, with the down payment already set aside and the notary's date marked. One of the two, usually with a certain clumsiness, raises seriously for the first time a question that had been floating around for months: if one puts up 70% of the down payment and we're both going to pay the monthly instalment, is the house ours 50-50? Or is it ours 70-30? And the instalment, 70-30 too?

The short answer, the one notaries give when asked, is that ownership can be set however the parties want, as long as it's documented. The long answer, the one that ought to be given before signing, is that choosing that proportion badly can cost a lot if the couple breaks up, if one of the two dies, or simply if twenty years go by and one wonders how much of the house is really theirs. Let's go step by step, because there are three concepts people mix up that aren't the same thing: the down payment, the monthly instalment, and the registered ownership percentage.

What gets mixed up and why it cracks when it isn't separated

The down payment is that cash that appears from savings to cover what the bank doesn't lend, which in recent residential mortgages usually runs around 20% of the property's price plus the associated costs (taxes, notary, registry, valuation), which in practice means between 25 and 30% of the appraised price in cash on the day of signing. For a home of 280,000 euros, that's between 70,000 and 84,000 euros on the table.

The monthly instalment is what gets paid over the following 25 or 30 years, and represents the sum of the capital amortised plus the interest, in a proportion that changes over time. And the registered ownership percentage is what literally appears on the deed: both partners at 50%, or one at 70% and the other at 30%, or any other combination.

The common mistake is to assume those three numbers must coincide. They don't have to. A couple can put up the down payment 70-30 from their savings, pay the instalment 50-50 for the next thirty years, and sign the deed 50-50 without anyone giving it a thought. The result, in terms of real ownership, is opaque: how much of the house is whose? It depends on how those unequal contributions are interpreted on the day things have to be settled.

Three models of splitting and what each implies

1. Deed at 50-50, instalment at 50-50, unequal down payment not documented

This is the most common model among young couples buying their first home. One puts up more of the down payment, usually because they came in with more savings, or because they received family help, and it's signed 50-50 "because we're a couple." The intention is lovely; the legal effect is that the difference in the down payment is considered, absent documentary proof to the contrary, a gift to the other member of the couple for half the difference.

If the couple stays together for life, this model generates no problem at all. If they break up two years later, and the difference was 30,000 euros of down payment, very hard conversations can play out about whether that was a gift or a loan, about whether there's any way to recover it, about whether it was family money that the family now reclaims. Adult couples decide this before signing; couples who trust without documenting anything decide it after the fact, in a worse emotional state.

2. Deed proportional to the down payment, instalment at 50-50

The one who put up 70% of the down payment appears as owner at 70%; the instalment is paid 50-50. Apparently fair on the day of signing, but with a detail: as capital is amortised with the monthly instalment, that capital is split in half between the two, and the registered percentage should be gradually adjusted over time if you want to reflect reality. In practice, the registered percentage isn't modified except through new deeds, so twenty years later real ownership may not look much like the registered ownership.

It's a clean model for couples who contribute differently at the start but understand that marriage or cohabitation functions like a financial partnership with separate accounts. It's not the most common, but it's the most honest.

3. Deed proportional to the expected total contribution

Some advisers recommend calculating what percentage of the total to be paid over the entire mortgage each contributes, counting down payment plus estimated instalments, and signing with that percentage. If one is going to put up 60% of the total over the next thirty years, they sign 60-40. It's mathematically consistent with the real economic effort, but it assumes the two people's relative incomes won't change in thirty years, which is a heroic assumption.

The monthly split of the instalment: the part people forget

Who pays what percentage of the monthly instalment depends, above all, on the income difference. A couple in which one earns 2,500 euros net and the other 1,500 can split 50-50 if they both prefer, but the second is devoting a much higher percentage of their salary to housing, and is going to feel it in everything else. The split proportional to income (62-38 in this example) is more sustainable in the long run, especially if there are children and one of the two can reduce their hours at some point.

The interesting note is that this proportion should be reviewed when incomes change. A promotion, a job change, a reduction in hours, a period of unemployment: all of them alter the balance, and keeping the initial split "because that's how we agreed it when we signed" stops being fair as soon as the circumstances change.

The invisible expense: special levies, taxes, and repairs

Beyond the instalment, a home you own generates recurring expenses that most couples don't budget for as housing. The annual property tax, which in a mid-size capital in 2026 runs between 400 and 900 euros for an 80-square-metre flat. The community fee, which in buildings with a pool or an old lift can climb to 80 or 120 euros a month. The home insurance, another 200 to 400 euros a year. The special levies, that unexpected surprise the owner pays when the lift has to be replaced, the façade repainted, or the gas installation renewed. And the home's internal repairs, from a boiler to a blind.

All of that should follow the same split criterion as the instalment. If the instalment is paid 60-40, the special levies are paid 60-40. Keeping track of this by hand year after year is the surefire recipe for forgetting half the amounts in the next awkward conversation.

A decent system should let you charge the monthly instalment at the agreed percentage, adjust it when incomes change, log the special levies and community expenses as shared expenses of the same group, and it distributes the cents by largest remainder, not by truncation, so that nobody always pays the rounding. ControlarGastos does exactly that, and it shows especially when they're four or five years into the mortgage and the inevitable question comes up of how much each one has contributed.

Conclusion: the adult conversation before the notary

Signing a mortgage with a partner isn't just a legal act, it's a thirty-year declaration of financial intent. And like any thirty-year declaration, it's worth making it in writing, in detail, before the emotions of signing day cloud the calculations. The difference between a couple who sit down one afternoon calmly to put in writing who contributes what and why, and a couple who sign 50-50 "because it looks better," shows up ten years later, not before. And it usually shows up in the kitchen, not at the notary.