Can I ask a genuine question regarding tax for locums. I have just joined the locum gp land few months back.

Some of the clinics that I locum in pay via Cash (usually the small family clinics in the neighborhood unlike the large chain groups)
- when I mean cash, I also include those that pay via bank transfer like paynow at the end of the shift. (I e the clinic owner/anchor just paynow me my pay at the end of the shift)

Do I need to declare these cash payments for tax? Given that this is a bank transfer between 2 parties with no cpf involved, how does iras track it?