These measures are put in place to help protect against online fraud, and to better secure your accounts and payments on CardUp. The OTP is a secure way to authenticate that the user setting up the online payment is the rightful owner of the credit card being used.
You also may see a SGD$0.50 pending charge on your bank statement as part of the card authorisation process but note that it is only temporary. This authorisation fee is needed to verify if the card is an active card, so rest assured that this charge will be refunded automatically within 7 to 14 working days (excluding Public Holidays and weekends)