PCT vs Paris Convention: Which Route Should You Choose?

When filing a patent internationally, there are two main routes: the Patent Cooperation Treaty (PCT) and the Paris Convention. Both allow you to file in multiple countries while claiming the same priority date — but they differ fundamentally in cost, timing, and flexibility.

This article breaks down the differences and provides a framework for choosing.

The Two Routes at a Glance

The PCT Route

The PCT is not a "world patent." It is a mechanism for deferring national filing decisions while preserving your priority date in more than 150 countries.

You file one PCT application within 12 months of your priority filing. WIPO publishes it and an International Searching Authority produces a search report assessing novelty and inventive step. At month 30 from your priority date, you choose which countries to enter — each requiring a national application, translation, local attorney, and fees.

The PCT's core advantage is time. The 30-month window (versus 12 months under Paris Convention) gives you 18 additional months to assess commercial traction, secure funding, evaluate competitor activity, and make informed decisions about which markets justify the cost of national prosecution.

The PCT also provides information. The International Search Report tells you — before you commit to expensive national filings — whether your claims are likely to be allowed. A negative search report may save you tens of thousands of dollars by discouraging national phase entry in marginal markets.

The cost: PCT filing fees are approximately $3,000–$5,000 (including search fees). National phase costs are additional — and are the same whether you arrive via PCT or Paris Convention. The PCT adds cost at the front end; it saves cost by helping you avoid unwise national filings at the back end.

The Paris Convention Route

The Paris Convention allows you to file directly in any member country within 12 months of your first filing, claiming the original priority date. There is no centralised application — you file separate national applications in each country, each with its own specification, translation, and fees.

The Paris Convention's advantage is directness and cost. If you know exactly which 1–2 countries you want to protect — say, only the US and China — filing directly in those countries avoids the PCT's upfront costs entirely. You pay only the national fees, and examination begins immediately.

The disadvantage is the compressed timeline. You must make all national filing decisions within 12 months. If you are uncertain about which markets matter, 12 months may not be enough time to assess commercial viability — and any country you miss is lost forever.

A Decision Framework

Choose PCT when:

• You plan to file in 3 or more countries
• You are uncertain which markets will be commercially important
• You want the ISR to inform your national filing strategy
• You need more time to raise funding for national phase costs
• You want to maximise optionality while minimising early commitment

Choose Paris Convention when:

• You are targeting only 1–2 specific countries
• You have a clear commercial strategy and know exactly where to file
• You want to minimise upfront costs
• You want examination to begin immediately at the target office
• You are filing in a country that is not a PCT member (very few, but notably Taiwan)

Many inventors use both. A common strategy is to file a US provisional (Day 0), file a PCT application at month 12 (preserving more than 150 countries for 30 months), and file directly in China via Paris Convention at month 12 (starting Chinese examination immediately, including a utility model for fast protection). This hybrid approach uses the PCT for optionality and Paris Convention for speed in priority markets.

Countries Not Covered by PCT

A small number of commercially relevant jurisdictions are not PCT members. The most notable is Taiwan — which requires direct national filing under the Paris Convention (or a bilateral agreement). Pakistan is also not a PCT member. In these cases, the Paris Convention is the only route.

Sources

1. WIPO PCT System — Complete guide to the Patent Cooperation Treaty filing system
2. Paris Convention — Full text of the Paris Convention establishing the direct filing route and priority right
3. WIPO PCT Contracting States — List of current PCT member states
4. EPO Euro-PCT Guide — Guide to entering the European phase from a PCT application