In most cases you do not need to actively 'claim' CPF cash top-up relief – it is granted automatically. When you make an eligible cash top-up to your own or a family member's CPF account, the CPF Board records the contribution and transmits the information to IRAS, which then reflects the relief in your income tax assessment for the relevant Year of Assessment.
To qualify, the top-up must be a cash top-up (not a transfer of existing CPF savings) made under the Retirement Sum Topping-Up scheme to the Special Account (for those below 55) or Retirement Account (for those 55 and above), or a cash top-up to a MediSave Account. It must be received by 31 December to count towards that year's relief.
When you file your income tax return, check that the relief appears in your Notice of Assessment; if a top-up you made is missing, you can raise it with IRAS with supporting records. Remember that the relief is subject to annual caps and to the overall personal income tax relief cap, so additional top-ups beyond the cap will not generate further relief.
Apexia can help you confirm eligibility, check that the relief has been applied, and plan future top-ups tax-efficiently.