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A Recurrent Reminder is used in Slips where getting a Response is very important, they can be configured to go out multiple times in a day or repeat on a day basis until a response is received. Recurrent Reminders start going out from the Slip Due date set during the creation of a Slip. Status of this can also be seen in the Reminders tab.
They are set in during the initial Slip creation page as shown below
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The number of times a Recurrent Reminder is sent can also be configured, for eg if Repeat Reminders is set to Every 1 Day for 5 times, a reminder will got out once every day for the next 5 days.