# MD for: https://www.mercadopago.com.uy/developers/pt/docs/subscriptions/integration-customization/payment-methods/proportional-amount.md

\# 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. > WARNING > > 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. !\[Basic-subscriptions\](https://www.mercadopago.com.uy/images/subscriptions/linea-cobro-EN-v1.png) To define a pro rata for subscriptions payments, send a POST to the \[/preapproval\_plan\](https://www.mercadopago.com.uy/developers/en/reference/online-payments/subscriptions/create-preapproval-plan/post) 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\`. > NOTE > > 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 \[/preapproval\_plan/{id}\](https://www.mercadopago.com.uy/developers/en/reference/online-payments/subscriptions/update-preapproval-plan/put) endpoint, change the value from \`false\` to \`true\`, and execute the request.