What shared money commits you to

Couples generally adopt one of three arrangements: everything in common, everything separate, or a joint account funded pro rata to income for shared expenses. None is legally superior, and each produces different effects.

What matters is not the choice but its explicit character. An arrangement adopted by default, because it was convenient at the start, is found ten years later with consequences nobody had envisaged.

It allows each holder to dispose alone of the whole of the funds, without having to justify their origin, and makes each jointly liable for any debit balance. The bank does not have to check the other's agreement.

In case of conflict, a holder can request the account be denounced, which turns it into a joint-signature account, or closed. Payment incidents, for their part, are liable to affect both holders.

Article 214 of the French Civil Code requires spouses to contribute to the expenses of the marriage in proportion to their means, which is not a half-and-half split. Article 220 makes them jointly liable for debts contracted for the upkeep of the household and the children's education, with three exceptions: manifestly excessive expenditure, hire-purchase agreements and loans, save for modest sums or the agreement of both.

Article 221, by contrast, guarantees banking autonomy: each may open an account in their own name alone, and the bank treats them as having free disposal of the funds. This autonomy settles relations with the bank, not relations between spouses, since the funds remain subject to the matrimonial regime.

PACS partners owe each other material assistance proportionate to their means and are jointly liable for everyday debts, with the same exceptions. Their default property regime has been separation of property since 2007.

Cohabitants owe each other nothing and are never answerable for the other's debts. That is a complete freedom, whose counterpart is that no contribution can be claimed in court, including after years of shared life.

Three documents settle most later disputes: proof of the origin of the funds that financed a purchase, the statement of shares matching the actual contributions in the deed of acquisition, and, under a community regime, the declaration of reinvestment where a community asset is financed by personal funds.

The last is the most technical and the most decisive. Without it, an inheritance invested in the couple's home can become impossible to disentangle at liquidation, and the compensation owed is hard to prove.