Do I get more interest if I top up my CPF in January vs in December?

Top up in January is better than end of the year..

For example, one can start to top up your medisave at the start of January to earn 4% interest if you have extra bonus or 13 month bonus..

CPF interest is computed monthly (i.e. if you top up SA in Jan, you earn 4%/12 each month starting from Feb), but credited and therefore compounded yearly. You will get more interests if top up in Jan vs in Dec.