When you invest using bank mandate, the earliest date you can invest is shown as 1 working day later. This could even be a couple of days later in case of weekends and bank holidays.
We use your bank mandate instructions to transfer money from your bank account. These instructions need to be sent to your bank in advance (real-time is not allowed) which is why when you use AUTO-PAY or FLEXI-SIP, your money can only be invested a day or two later than today.
Our system debits your account for AUTO-PAY and FLEXI-SIP using this logic