Proportional amount (proration) - Customization of payment types - Mercado Pago Developers
Which documentation are you looking for?

Do not know how to start integrating? 

Check the first steps

Proportional amount (Pro rata)

Pro rata is the amount billed to the subscriber if the subscription starts on a day other than the billing date set by the seller. When creating a subscription, the seller can decide whether or not to offer this option.

Important
To set a proportional value, the fields frequency and frequency_type need to be filled with the values frequency:1 and frequency_type:months respectively. This means that the proportional calculation is only applicable to monthly subscriptions during a 30-day period.

Below we show a flow of how the proportional collection of payments works.

Basic-subscriptions

To define a pro rata for subscriptions payments, send a POST to the /preapproval_plan endpoint with the parameters billing_day and billing_day_proportional and execute the request. The first parameter accepts values from 1 (one) to 28 (twenty-eight) and must contain the day of the month in which the charge will be made. The second in turn must be sent with the value true.

Important
If you want to modify a specific subscription and define a Pro Rata, send a PUT with the billing_day_proportional parameter to the /preapproval_plan/{id} endpoint, change the value from false to true, and execute the request.