Calculate SBI recurring deposit maturity with the published SBI RD rate band selected from your tenure and customer type.
Why does this use the term-deposit rate table for SBI RD?
Because SBI's RD page says the rate of interest is the one applicable to term deposits for public and senior citizens. This page follows that published instruction and names the band it selected.
Why is the minimum tenure 12 months here?
Because SBI's RD page says the period of deposit is minimum 12 months and maximum 120 months. A shorter figure is not an SBI RD on the published product terms.
Why does the booking date matter for an RD?
Because the bank can revise rates. The booking date tells the calculator which published SBI rate version applies to the start of your RD, instead of smearing one current rate over every past booking.
Does this include default penalties?
No. It assumes every instalment is paid on time. SBI's RD page also publishes separate penalty rules for delayed instalments and premature closure.
What is the hard part here compared with a generic RD calculator?
Not the compounding formula. That is shared and already tested. The hard part is the dated bank-rate selection and the exact boundary where one tenure stops and the next one starts.