The Supplementary Protection Certificate (SPC) is a sui generis form of legal protection that extends protection conferred by a patent (called "basic patent") in respect of a medicinal or plant protection product.

In general, after filing a patent application the patentee can exploit the solution of the invention unlimitedly, he can place the product of the invention on the market. However, in the case of medicinal and plant protection products patent protection is reduced since the exploitation of the new product has to be postponed until authorization for placing the product on the market is received from the health and agricultural authorities. This period of time considerably reduces the protection period conferred by the patent, and the period of effective protection is insufficient to cover the investment put into the research and development and other investments. Accordingly, the patent does not encourage such research. To eliminate the penalization of these sectors, of the European Communities has adopted Council Regulation (EEC) No 1768/92 creating a Supplementary Protection Certificate for medicinal products, and the European Parliament and the Council have adopted Regulation (EC) No 1610/96 creating a Supplementary Protection Certificate for plant protection products with the aim of compensating the patentees for the loss of effective protection.

A certificate extends the protection conferred by the basic patent only to the product covered by the authorization to place the corresponding medicinal or plant protection product on the market, and to any use of the product as a medicinal product that has been authorized before the expiry of the certificate. The certificate confers the same rights as conferred by the basic patent and is subject to the same limitations and the same obligations.

The certificate takes effect at the end of the lawful term of the basic patent for a period equal to the period which elapsed between the date on which the application for a basic patent was lodged and the date of the first authorization to place the product on the market in the Community, reduced by a period of five years. The duration of the certificate may, however, not exceed five years from the date on which it takes effect.

This special calculation method ensures that the product covered by the basic patent enjoys an overall maximum of fifteen years of adequate and effective protection and furthermore a uniform solution at Community level is provided.