What is the difference between the EPC and the PCT?
The Patent Cooperation Treaty (PCT) and the European Patent Convention (EPC) are two of the most important international patent frameworks, but they operate at different levels and serve distinct functions. The PCT is an international treaty administered by WIPO that allows applicants to seek patent protection simultaneously in a large number of countries by filing a single international application. The EPC, by contrast, created the European Patent Office (EPO) as an independent authority that harmonizes European patent law and actually examines and grants patents across its member states.
Practitioners frequently encounter both systems in the same matter. A client seeking protection in both Europe and other major markets will typically engage the PCT and the EPC in sequence, not as alternatives.
The PCT: a global filing gateway
The PCT currently has 158 Contracting States, making it the broadest international patent filing framework in the world.
A central fact about the PCT that clients frequently miss: the PCT does not grant patents. The granting of patents remains under the control of the national or regional patent offices. What the PCT provides is a coordinated international phase, which includes an international prior art search by an International Searching Authority (ISA) and a written opinion on whether the invention appears to meet patentability criteria. The search report and written opinion give applicants early intelligence on claim strength before they must commit to the cost of national or regional prosecution.
After the international phase, PCT applicants must enter the national phase by filing with individual national or regional patent offices in each jurisdiction where they seek protection. A PCT filing, standing alone, produces no granted patents anywhere.
The EPC: a European grant system
The EPC was adopted on October 5, 1973, and entered into force on October 7, 1977. Its Contracting States span both EU and non-EU European countries, including Switzerland, Norway, the United Kingdom, and Turkey.
Unlike the PCT, the EPC is not a filing coordination or deferral system: it harmonizes substantive and procedural patent law across its member states and created the EPO as an independent authority with the power to grant patents completely independent from national patent offices. The EPO examines applications, issues office actions, and grants or refuses patents through its own examination procedure. This is the structural difference that matters most: the PCT facilitates filing across many countries without itself examining or granting anything, while the EPO is an actual examining and granting body.
What the EPO grants: bundle patents and the Unitary Patent
A traditional European patent granted by the EPO takes effect as a bundle of national patents that must be managed and enforced individually in each designated member state. After EPO grant, the patentee must validate separately in each chosen EPC member state, and states where validation is not completed provide no protection.
Since June 1, 2023, applicants have had an additional option: requesting unitary effect after EPO grant, resulting in a single Unitary Patent with uniform protection across participating EU member states, without the need for per-country validation.
How the PCT and EPC relate to each other
The two systems are complementary, not competing. The EPC is a special agreement under Article 19 of the Paris Convention and a regional patent treaty under Article 45(1) of the PCT. That classification means PCT applicants who designate European protection can enter the European regional phase at the EPO: the PCT application is processed as a European patent application under the EPC, and a European patent can be granted on the basis of the international PCT filing. This combined route, sometimes called the "Euro-PCT" route, is the most common path for international applicants seeking European patent coverage as part of a broader global filing strategy.
Side-by-side comparison
| PCT | EPC | |
|---|---|---|
| Administered by | WIPO | European Patent Organisation (EPO) |
| Contracting states | 158 (global) | European states (EU and non-EU) |
| Grants patents? | No | Yes, through the EPO |
| Primary function | Coordinated international filing and prior art search | Unified European patent examination and grant |
| Output | Deferred national/regional applications | European patent (bundle or Unitary Patent) |
| Relationship to the other | Global framework; covers all regional systems | Regional treaty recognized under the PCT |
Practical notes for practitioners
- A PCT filing is not a European application. Entering the European regional phase at the EPO is a separate required step. Without that step, a PCT application designating all states produces no enforceable European patent.
- Validation is a post-grant obligation, not an automatic result. EPO grant is not the end of the process for a traditional European patent. The patentee must validate separately in each member state where enforcement is wanted, or protection there lapses.
- The Unitary Patent simplifies post-grant management. For clients needing coverage across many EU member states, the Unitary Patent option eliminates per-country validation in participating states and consolidates renewal fees.
- Do not equate EPC membership with EU membership. The EPC includes countries that are not EU members, and the Unitary Patent covers only those EU member states that have ratified its enabling agreement. Verify the specific country set that matters for each client rather than assuming any one label covers the needed markets.
- The PCT international search informs European prosecution. Because a PCT application can enter the European regional phase at the EPO, the international search results and written opinion are available before EPO examination begins, giving applicants an opportunity to refine claims before committing to European prosecution costs.