An aggregator, or payment aggregator, is a merchant service provider that allows businesses to accept card payments without having to set up a merchant account. Instead, the aggregator combines all of its clients into one large merchant account that it manages on their behalf. Examples of aggregators include companies like PayPal, Square, and Stripe.

This model can be a quicker and more convenient way for small businesses and individuals to begin accepting card payments.

Aggregators work with a variety of businesses and process their payments as a single entity. They play an important role in the payment ecosystem by providing a simple, easy-to-use solution for businesses that may not have the resources or need to manage their own merchant account.

However, there can be downsides to using an aggregator. For instance, because the aggregator is essentially assuming the risk for all the transactions it processes, it may hold funds or terminate accounts if it detects what it considers to be suspicious activity.

Aggregators may have higher transaction fees compared to traditional merchant accounts.