CPF Annual Limit - Do I consider the month the monies hit CPF account or salary month?

I am trying to estimate if I will hit CPF Annual Limit for calendar year 2021 before making any top up to SA (monthly salary exceed $6K). I am also include upcoming leave encashment and bonus in Dec 2021.

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CPF says the maximum amount one can voluntarily top up is the difference between the CPF Annual Limit of $37,740 and the mandatory CPF contributions made for the calendar year.

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Can I check if this goes by transactions in the calendar year? E.g Salary+bonus+leave encashment received for the month of Dec 2021 and contribution is credited to CPF account by mid Jan 2022. Do I include this in my estimation for CY2021 or is this considered in CY2022 since the amount will hit the account in Jan 2022.

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Thank you.