Das scheint einfach zu heißen, dass die Gutschrift nur einmal gewährt wird, also nicht voll pro sorgepflichtigem Elternteil, wenn beide das Sorgerecht haben. Guckt man die Regelung für Ehepaare nach (z.B. hier: http://www.admin.ch/ch/d/sr/831_10/a29sexies.html ), sieht man, wie das praktisch läuft:
"Bei verheirateten Personen wird die Erziehungsgutschrift während der Kalenderjahre der Ehe hälftig aufgeteilt."
Bei anderen Situationen (z.B. Geschiedene mit gemeinsamem Sorgerecht) wird die Anrechnung demnach gesondert geregelt.

Might be. It is quite difficult to understand what exactly is the text saying. What are these "Beiträge" about? Is that something you receive, or something you pay?

Well yes, combined, but I think cumulated fits better in English, too...

It means that that Erziehungsgutschrift (must be some kind of child allowance.. I'm Swiss, but I'll have to admit though, I never heard of that.) is only paid out once if two people are parenting a kid, even if they both would be entitled to that allowance otherwise...

To comulate:
I think cumulate is way less common in English than accumulate. In German we use both, and although I'm not 100% sure, I think the difference is that when cumulating, the two or more things to be cummulated "arrive" in the cummulation location at the same time. When accumulating, the three or more things come staggered and are then amassed.

Thanks for the explanation, I'll find some workaround based on it. Cumulate might be a word in English, but I doubt anyone would understand what it means in this context.

P.S. Erziehungsgutschriften are credits that are awarded to your retirement assets for taking care of kids under sixteen.