International patent filing means seeking patent protection in countries beyond your home jurisdiction, either by filing directly in each country under the Paris Convention or by filing a single PCT application that preserves the option to enter multiple countries later. Since patents are territorial, protection only exists in countries where a patent has actually been granted.

There's no such thing as a single global patent; "international patent" usually refers to a PCT application, which preserves the option to seek protection in over 150 member countries but still requires separate national-phase filing and examination in each one. Full international protection means holding separate, granted patents in each country where you want enforcement rights.

The most common route is filing a PCT application within 12 months of an initial priority filing, which delays the decision of exactly which countries to enter for up to 30 months. Alternatively, direct filing in specific countries under the Paris Convention within that same 12-month window is faster and cheaper when only one or two countries are needed.

A PCT (Patent Cooperation Treaty) application is a single international filing that preserves the option to seek patent protection in over 150 member countries, without granting a single worldwide patent itself. It gives applicants up to 30 months from the priority date before committing to specific national filings.

Think of a PCT application as buying time and keeping options open internationally, rather than as a patent itself. It delays, but doesn't replace, the eventual need to file and get examined in each specific country where protection is wanted.

PCT filing typically costs $3,000 to $5,000 in international fees, separate from the priority application it builds on and the national-phase filings that follow later. Some fees receive entity discounts, but the core international filing fee paid to WIPO is the same for every applicant.

A European patent is obtained through a single application to the European Patent Office (EPO), examined once and, if granted, validated in the specific European countries the applicant chooses, or registered as a single Unitary Patent covering most EU member states. It reduces duplicated examination compared to filing separately in every European country.

Filing with the European Patent Office lets an applicant pursue patent protection across many European countries through one examination process rather than filing nationally in each one. It works alongside the PCT system as one common route into European protection.

A UK patent application can be filed directly with the UK Intellectual Property Office, via a European patent application designating the UK (the UK remains a full member of the European Patent Convention, which is separate from the EU), or through PCT national phase entry. The UK is not part of the EU's Unitary Patent system, so a Unitary Patent doesn't cover the UK; a granted European patent must be validated in the UK separately.

Foreign applicants file with the USPTO the same way domestic applicants do, either directly, via the Paris Convention within 12 months of a home-country filing, or through PCT national phase entry. US patent agents or attorneys are generally required to represent foreign applicants before the USPTO.

Both countries can be entered directly under the Paris Convention within 12 months of a priority filing, or via PCT national phase entry, each requiring separate national examination and fees. Local patent agents are typically required to prosecute applications in-country.

Beyond the original priority filing, a PCT application costs $3,000-$5,000, and each country entered at national phase adds its own filing, translation, local attorney and renewal costs. Over a patent family's lifetime, protection across the key economies most companies prioritise (the US, Europe, the UK, China and Japan) commonly totals $50,000 to well over $100,000, and filing more broadly pushes well into six figures, which is why most companies protect their largest markets rather than filing everywhere.

Yes, filing directly in specific countries under the Paris Convention within 12 months of a priority application is a valid alternative, and can be cheaper and faster when you already know exactly which one or two countries you need. The PCT becomes more cost-effective once three or more countries are under consideration.