Short answer. When the Family Code's chapter on absolute community of property is silent on a particular matter, the Civil Code's provisions on co-ownership step in to fill the gap. Article 90 of the Family Code makes this explicit: co-ownership rules apply suppletorily in all matters not covered by that chapter.
What the law says
The provisions on co-ownership shall apply to the absolute community of property between the spouses in all matters not provided for in this Chapter.
Family Code, Article 90 — Co-ownership Rules Apply Suppletorily. Read the full provision →
The gap-filling rule under Article 90
Article 90 of the Family Code provides that the provisions on co-ownership shall apply to the absolute community of property between the spouses in all matters not provided for in this Chapter. This is a suppletory rule — it does not apply when the Family Code itself has already addressed the issue. But whenever a situation arises that the ACP chapter does not specifically regulate, the Civil Code's general co-ownership framework automatically steps in to govern that gap.
How suppletory application works in practice
The absolute community of property is the default property regime for spouses who marry without a prenuptial agreement. The Family Code chapter on ACP covers the main questions — what assets go in, what assets are excluded, who can administer the community, how it is dissolved, and how it is liquidated. When a question falls outside those regulated areas, a court or the spouses themselves look to the Civil Code provisions on co-ownership for the answer. This might arise, for example, in disputes over how a jointly owned asset should be used, maintained, or preserved when the Family Code has not prescribed a specific rule.
Why co-ownership is the chosen reference
The absolute community of property is, at its core, a form of shared ownership: both spouses own all community assets together, in undivided shares. Because its structure resembles co-ownership, it makes logical sense for the legislature to use co-ownership principles as the default framework. The Civil Code's co-ownership rules address management, use, expenses, improvements, and division of common property — all of which are relevant concerns between spouses who share a pool of assets. The suppletory reference prevents gaps in the law from leaving spouses without any legal guidance.
Limits of the rule
Suppletory application does not mean co-ownership rules override the ACP chapter where the Family Code has spoken. If the Family Code expressly regulates a matter — such as administration of community property, alienation of community assets, or the effect of dissolution on the regime — those provisions control and co-ownership rules do not displace them. The reference to co-ownership is a safety net for genuinely unaddressed situations, not a licence to ignore what the Family Code has already said. If you are facing a specific dispute about community property and are unsure which rules apply, the facts matter significantly and legal advice is warranted.