post https://sandbox.asaas.com/api/v3/subscriptions
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When creating a subscription, the first monthly installment will be generated with a due date set to the date provided in the nextDueDate parameter.
Can I create subscriptions with a free period?
If you work with a trial period (7 days free, for example), you can follow the same form and enter the data for the first charge in the nextDueDate field. Thus, if the card is validated upon creation, it will already be saved so that the first payment takes place on the day you inform.
However, if you create a subscription without card details and the payer enters it after the card details, the amount will be deducted the moment they insert the card, regardless of the nextDueDate.