It's not totally about carseat but a new regulation goes into effect this August. I don't think there's any English version yet, so I'll just highlight what's new in Taiwan.

Starting August 1, 2011, all passengers in the backseat must buckle up, let it be in the car, taxi or van.

There will be a 6-mo to 1-yr campaign/transitional period. so people won't be fined until:

1. Feb 1, 2012, if you are an adult who fails to obey the rule.
2. Aug, 1, 2012, if you are a children under 12 without a seatbelt. Carseat implementation when age and/or height appropriate.

Fines (in NTD$) are followed:
1. $1500 fine to the car driver when driving in local;
2. $3000 to $6000 when driving on highway or expressway.
3. For cab riding: passengers will be fined when refusing to buckle up. Children 4 thru 12 year old are exempt.

Hope this help those who will be visiting Taiwan & drive safe.