The central clearing obligation does not apply to every class of OTC derivatives. The central clearing obligation applies to the most common forward rate agreements and interest rate swaps, overnight index swaps and some index-based credit default swaps.
The European Securities and Markets Authority (ESMA) decides which classes of derivatives have to be cleared centrally. The main requirements for products to be centrally cleared are their standardization, liquidity and suitability for risk management/modelling. ESMA has an updated list of in-scope OTC derivatives on its website here .