Indexing child support in France in 2026: the formula and the INSEE indices
Every year support follows prices: the formula fits on one line, as long as you use the right indices.
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French child support is almost always index-linked: most judgments and agreements include a clause (“clause d’indexation”) so the amount keeps its value as prices rise. The official formula is simple: amount × new index ÷ base index. The new index is usually the latest one published in the Journal officiel on the indexation date; the base index is the one in force on the date of the decision. Service-public.fr gives the example of €300 set on 4 June 2020 and indexed on 1 January 2026 with the urban households index: 300 × 100.03 ÷ 87.07 = €344.65. It is up to the paying parent to do the sum every year, without being asked. The calculator below uses that example; replace the values with those of your own judgment.
Index the support with the INSEE figure
New monthly amount
€344.65
| Increase per month | €44.65 |
| Increase over a year | €536 |
| Change | 14.9 % |
November 2025 indices, valid on 1 January 2026
| Consumer price index excluding tobacco, base 2025 | November 2025 |
|---|---|
| All households, France | 99.87 |
| Urban households headed by a manual or office worker, France | 100.03 |
For an indexation on another date, the right index is the latest month published by that date (the Journal officiel publishes a month’s index around the middle of the following month). INSEE’s website has a calculator and the full series; always check that the base index and the new index are on the same base.
What indexation adds up to over the years
| Base index | New amount | Gain per month |
|---|---|---|
| 87.07 | €344.65 | €44.65 |
| 92 | €326.18 | €26.18 |
| 95 | €315.88 | €15.88 |
| 98 | €306.21 | €6.21 |
The first row is service-public.fr’s example; the others use illustrative base indices to show how the age of the judgment matters. Support that is never indexed loses value and builds up a debt to the other parent: see child support arrears.