Learn Spanish (Latin America): Es mejor que aportes la cuota cuando recibas la invitación. - It is better that you contribute the fee when you receive the invitation.

The phrase Es mejor que (It is better that) expresses a subjective opinion or recommendation. In Spanish, these types of impersonal expressions require the verb that follows them to be in the subjunctive mood. That's why we use aportes instead of the normal present tense aportas.

Why do we use the subjunctive recibas after cuando?

The word cuando (when) can take either the indicative (normal present tense) or the subjunctive, depending on the meaning. If you are talking about a routine (like "when I receive emails, I read them"), you use the indicative. But because this sentence talks about an event that hasn't happened yet (receiving this specific invitation in the future), cuando must be followed by the subjunctive recibas.

What exactly does aportar mean here instead of just saying pagar?

Aportar means "to contribute" or "to provide." While pagar (to pay) describes a standard transaction, using aportar implies you are pitching in your share to a collective fund, group effort, or shared expense.

What is a cuota in this context?

La cuota usually means a "fee," "dues," or "share." It is often used for the specific amount of money each person needs to chip in for a shared cost, like a monthly club membership, maintenance fees, or an event.