Hi @nandini29,

Have a script in a Flow Variable to fetch 25th of very month and return the date.

var now = new GlideDateTime();
var target = new GlideDateTime();

// Set target to the 25th of the current month
target.setDayOfMonth(25);

// If the 25th has already passed, move to next month
if (target.compareTo(now) <= 0) {
    target.addMonthsLocalTime(1);
    target.setDayOfMonth(25);
}

return target.getValue();

Use the wait-for-duration activity, change the duration type to relative duration, and then used 1 second after the flow variable value to make the flow until the specified time and then triggered the next action. 

Its best if you trigger Flow from Scheduled Job which has low code setting for running on 25th of every month.

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Kind Regards,

Ehab Pilloor