Preliminary look at the legal framework of European countries regarding ONLY property rights in cohabitation, NOT redress.
As one will see today only Croatia, Finland, Ireland, Slovenia, Sweden and somewhat UK regulate de facto families akin to marriage regarding property.
Austria
There are no special property rights provisions for unregistered extra-marital cohabitations, and an analogous application of §§ 81et seq EheG on the property division after dissolution of the marriage has been rejected by the legal practice. The general provisions of the law of obligations and of property law are applied.
Belgium
In the case of unregistered partnerships (In Belgian law: cohabitation de fait/feitelijke samenwoning), there exist only the two separate estates of the partners.
For each debt that is entered into by one of the registered partners for the purpose of the cohabitation, the other partner is also jointly and severally liable (Art. 1477 CC). This is not the case for an unregistered partnership.
Upon the death of one of the partners, the surviving partner from a registered partnership receives the usufruct of the real estate that serves the family as common residence including the household assets (Art. 745octies CC). This is not the case for an unregistered partnership.
Registered partners can regulate their partnership by means of an agreement. In conformity with Article 1478 in fine CC, such agreements must be established by notarial act.
Bulgaria
Only civil marriage, concluded in the form prescribed in the Family Code, shall have the proprietary effects that the laws provide for marriage.
Croatia
According to the Family Act, an extramarital union is a union between an unmarried woman and an unmarried man that lasts at least three years or less under the condition that a child has been born during the period of cohabitation (Article 11 of the Family Act).
Croatian law does not provide for the registration of an extramarital union. The court shall decide if all preconditions have been met for an extramarital union in each individual case. The same provisions of the Family Act as for spouses apply to an extramarital union between a man and a woman meeting the preconditions set in Article 3 of the Family Act).
Cyprus
There is no law governing cohabitation without marriage in Cyprus; Cypriot family law refers exclusively to married couples. No provisions currently exist with respect to the matrimonial property of persons who are not married. It is, however, accepted that the law of equity concerning constructive trusts may apply to unmarried partners. Thus, a partner may have rights if it can be proved that there was common intention with respect to an asset and the partner can prove that he/she was a beneficiary of such an asset in accordance with the general principles of constructive trusts.
Czech Republic
Czech law does not provide for any specific property regime for registered partners. Nevertheless, registered partners are free to regulate their property relations by a contract. The same applies for non-registered partnerships. Nevertheless, in the course of succession, the surviving registered partner and the deceased’s children inherit in the first order of succession, each of them in equal parts (Section 1635 para. 1 and Section 3020 of the Civil Code).
Denmark
The Nordic Convention on Marriage is inapplicable to registered partnerships. (Registered Partnership Act, § 1 and §§ 3-4)
Nothing's written on unregistered.
Estonia
Under Estonian law cohabitation cannot be registered and there is also no other special regulation foreseen for nonmarital cohabitation. Nonmarital cohabitees can use other legal means outside of family law: they can form partnerships under the law of obligations (the application of implied contracts is limited only to the movable property), acquire common ownership over property according to the law of property, make wills according to the law of succession etc.
Finland
If the non-registered partnership has lasted for less than five years, and the partners do not have a common child, disputes over the partners' property are solved on the basis of the general legal provisions. For example, if a non-registered partnership has ended, a partner can claim the return of an unjustified benefit. Other practically relevant legal remedies are claims for payment, verification of ownership, and restitution of possession. If the non-registered partnership has lasted for longer than five years, or if the partners have or have had a common child, the "Act on the dissolution of the household of cohabiting partners", which took effect on 1 April 2011, is applicable. According to this act, after the partnership has been dissolved, a partner is entitled to receive compensation from the other partner if he/she has helped the other partner to accumulate or retain his/her property with the contribution that he/she has made for the benefit of the common household
France
Unregistered partnerships (cohabitation) are recognised by Art. 515-8 CC but are not regulated.
Registered partnerships (civil partnerships - French PACS) are regulated by Art. 515-1 CC et seqq. These partnerships are available to same-sex (as well as opposite-sex) couples. Civil partners are jointly and severally liable for debts contracted by one of the partners for "everyday needs" (Art. 515-4 CC).
Germany
Nothing's written on unregistered.
Greece
4) There are no provisions regulating the property rights of unregistered partnerships.
Hungary
Nothing's written on unregistered.
Ireland
The The Civil Partnership and Certain Rights and Obligations of Cohabitants Act 2010 (2010 Act) provides for the creation of a Civil Partnership Registration Scheme (for same sex couples) (Parts 1-14 and Part 16) and for a Cohabitants’ Redress Scheme (for same sex and opposite sex couples) (Part 15) which does not require registration.
Italy
Nothing's written on unregistered.
Latvia
Latvian law only recognizes the marriage between heterosexuals. There are no laws regulating registered or unregistered partnerships.
Lithuania
Provisions of the Civil Code of the Republic of Lithuania on cohabitation without registration of marriage or on registered partnerships have not yet entered into effect.
Luxembourg
There are no special provisions regarding the property regime of non-registered non-marital unions.
Malta
The newly enacted Cohabitation Act, Chapter 571 of the Laws of Malta, makes special provisions for the ‘ordinary, primary, common home’ only in the case of registered partnerships.
Netherlands
The BW contains no regulations for unregistered cohabitants.
Poland
There is no legal regulation on registered or unregistered partnerships.
Potugal
Portuguese law does not contain any special provisions on the property relations of partners. The general provisions of the law of obligations apply.
This is outdated as "On 9 July 2010, de facto union expansion law (that included inheritance rights, compensation and other benefits) passed the Portuguese Parliament." https://en.m.wikipedia.org/wiki/De_facto_union_in_Portugal?fbclid=IwAR3ndA6ARJbU0cm544vFCuRXLuLd4eT9mA7IMIZV24VR3fXNmV9-Ul2F1Ok
Romania
Registered or non-registered partnerships are neither acknowledged nor regulated by Romanian law.
Slovakia
The Slovak legal order does not recognize registered or unregistered partnerships.
Slovenia
Cohabitation is defined as a long-term relationship, similar to the marital relationship, between two heterosexual partners who could marry if they so wished. This means that there must not be any legal obstacles to their marriage. The property regime for cohabiting partners is equivalent to the property regime for spouses. Thus common property is formed in the same way as for married couples. Registration is not possible for heterosexual partners. As it is almost impossible to determine when a relationship becomes long-term, all assets acquired after the partners began living together shall constitute common property, in cases where there would be no obstacles to the couple marrying.
Spain
There are no specific legal provisions on property for unregistered extramarital partnerships...
In the absence of any agreement or any specific legal provision, the general provisions of the law of obligations and of the law of property will apply.
Unless otherwise provided, the family home belongs to the owner, unless there are children or an interest in need of protection, in which case the judge will decide.
Sweden
Cohabitation outside marriage In Swedish law cohabitation outside marriage is regulated by a special law: the Cohabitees Act (2003:376). The Cohabitees Act applies to two unmarried persons of the same or different sex, living permanently together in a relationship and sharing the same household. The law is intended as a protection regulation for the financially weaker party, and no registration of the relationship takes place. When cohabitation ends § 2), either party may request the division of property within one year (§ 8). Division of property rules according to the Cohabitees Act are based on the division rules of the Marriage Code. However, the property which may be subject to division according to the Cohabitees Act is much less extensive, in that only the cohabitees’ joint home and household goods which are purchased for joint use may be subject to division (so-called cohabitee property).
UK
England/Wales
There is no specific regime for couples living together without having formalized their relationships (usually referred to as 'cohabitants') who will therefore have to rely on the general law, and particularly the (common intention) constructive trust (see especially Jones v. Kernott [2011] UKSC53). It is important to note, however, that the courts have considerable discretion to make orders with regard to the children under Schedule 1 of the Children Act 1989 (entitled 'Financial Provision for Children'), including lump sum payments and property transfers.
Scotland
For unmarried couples cohabiting as husband and wife (or unregistered partners cohabiting as civil partners) the rules applying during the relationship are the same as set out above for married couples but the rules on split-up and death are different. There is no principle of equal sharing of matrimonial property on split-up and there are no fixed survivor's prior rights or protected legal share on the partner's death. However, the cohabitant can apply to a court for a financial provision on the split-up (designed mainly to rectify any injustice caused by contributions made or disadvantages suffered in the cohabitation) and for a discretionary provision on the death of the other partner (see sections 25 to 29 Family Law (Scotland) Act 2006).