What happens if my CPF contribution exceeds the annual limit?

CPF has 2 wage ceiling limits.

Firstly, the Ordinary Wage Ceiling which limits the amount of OW that would attract contribution and is capped at $6000 currently. If you earn $7000, the first $6000 would be subjected to CPF contribution. The remaining $1000 is not subjected to CPF contribution (This includes your employer which will not be required to contribute to your CPF for any amount above $6000)

Next. the Additional Wage Ceiling caps your yearly limit to $102,000 - Total OW for that year currently. Additional Wage are things like annual bonuses etc. Any amount above this sum will not be subjected to CPF contributions.

If you did voluntary contributions, you will get a refund of the excess voluntary contributions without interest.

As for mandatory-only contributions, I'm not sure if the excess comes out immediately as cash.