We must challenge SCB. Have a look at the T&C:
http://www.wowmanhattan.com.sg/pdf/Y18608_299106_SCB_MANHATTAN_A4_Placemat_LR_NC.PDF
The exclusions even include "Refunds credited back (eg. tax refund)". But not tax payment..
The inclusions include "Online bill payments via merchant’s websites". The mobile axs payment should come under this
https://www.sc.com/sg/campaign/manhattan/
You (and/or your supplementary cardholder(s)) will not earn cashback on the following transactions:
any cash advance,
any fees and charges (including annual fees, late payment fees, interest charges, and or finances charges) charged to your Credit Card,
any balance or fund transfer,
any monthly instalment of an EasyPay transaction,
any amount charged to your Credit Card (and/or your supplementary Credit Card) that is subsequently cancelled, voided, refunded or reversed,
recurring payments or payments made to all billing organisations using Standard Chartered Online Banking,
AXS or ATM transactions made using the Credit Card,
amounts which have been rolled over from the preceding months’ statements,
tax refunds credited into your Credit Card account (and/or your supplementary Credit Card account),
any insurance premiums charged to your Credit Card and
any other charge, fee, transaction or payment as we may stipulate from time to time. We may at any time vary, revise or change any Terms and Conditions at our sole discretion.