"AMCs prescribe a list of their schemes in which you can invest through SIP. They specify the frequency of SIP, mention the specific dates in a month on which your SIP request can Start and also mention the minimum number of SIP instalments.
For e.g. an AMCs may offer the following:
Frequency: Monthly, Quarterly and Yearly
Start Date: 1, 8, 15, 22 (of every month)
Minimum Period: 12 months
You chose a quarterly SIP to be started on 8-Feb-12. Since the minimum period is 12 months, you would be required to pay 4 SIP instalments in a year. Your SIP would be debited on the 8th of every quarter i.e. 8-Feb-12, 8-May-12, 8-Aug-12, 8-Nov-12."