Which International Searching Authority should you choose? A guide for non-European applicants

May 19, 2023

For international (PCT) patent applications a number of different International Searching Authorities (ISAs) are available to undertake international searches. Which ISAs are available depend on the nationality or residence of the applicant.

When choosing an ISA there are many different factors to consider and it is unlikely that one size fits all.

The EPO is available as ISA for most countries, including US, China, India and Japan.

US applicants can currently choose from: the USPTO, the EPO, Korea, Australia, Israel, Japan and Singapore (Russia is no longer an option). According to the WIPO IP Statistics Data Center from 2022 to 2023, PCT applications filed with the US Receiving Office used the following top three ISAs: EPO 41.6%, USPTO 37.8%, Korean 13.3%.

UK applicants, on the other hand, can only choose the EPO as ISA.

Some factors in deciding which is the best ISA for your circumstances are as follows:

Cost and Applicant Size

The EPO is one of the more expensive ISAs (currently $1875).

Unlike other ISAs, the USPTO has different fees depending on entity size. For large entities the cost ($2180) is larger than the cost at the EPO. For small entities the cost is significantly less ($872). For micro entities the cost is smaller still ($436) and is currently the lowest available to US applicants.

Korea is a relatively lost cost option ($924), which is cheaper than the USPTO for large entities.

Therefore, for smaller applicants the USPTO may be a more attractive option. Whilst for larger applicants other ISAs may be more attractive.

Cost Savings in the National Phase

The above analysis only considers the fees at the international phase. When national/regional phase costs are factored in, the picture can change significantly.

If a US applicant intends to elect Europe for national/regional phase entry, the EPO usually makes the most sense for ISA, especially for large entities. This is because when the EPO is the ISA there is no regional phase search fee payable. Leading to a discount of €1460 ($1580).

The US and Korea also offer discounts when selected for both the ISA and for national phase entry. In the US, the discount varies based on the applicant size and the issues identified in the written opinion. This can result in a discount of up to $1500. However, many US applicants file PCT applications after already having filed a patent application in the US. As such they would not enter the US national phase and therefore would not be taking advantage of such a discount.

Korea offers a 70% reduction on the demand fees for examination. However, since this fee is already very low, the discount results in negligible savings.


The quality of a search is, of course, subjective. The EPO is usually seen as the gold standard for searches.

USPTO ISA searches are outsourced to a private company and are not performed by the same examiners as US patent applications. As such, in the national phase USPTO examiners may not give full weight to outsourced searches and written opinions, they instead prefer to make their own decision.

One factor to consider is the effect of the language skills on what the searcher may find. US searchers often only read English. Korea searchers read Korean, English and usually Japanese. EPO searchers read English, German, and French, and possibly some additional languages. In certain subject areas, prior art may be suspected to exist only in certain languages and so choosing an ISA whose examiners read that language is likely to be beneficial.

Poorer quality searching can lead to negative search results only being found once an application has progressed to the national or regional phase and significant extra costs have occurred.

Subject matter

The EPO searches international applications the same as for European applications. This will result in searches not being carried out in certain areas. In particular, the EPO states that it will not act as ISA for applications where one or more claims relate to business methods. Thus the EPO should not be selected as ISA for applications where this is a significant risk.


Different ISAs tend to take different views on unity of invention, and so the number of inventions claimed should be factored into the decision of which ISA to choose.

A unity objection can lead to further search fees being payable which can significantly increase the cost. The costs for additional search fees are usually the same or similar to those for the initial search.

Generally, the EPO is seen as being stricter on issuing unity objections than the USPTO and so might be avoided if such an objection is seen as being likely.

Speed of subsequent prosecution

The USPTO, the EPO, Japan, Korea and China are part of the IP5 patent prosecution highway (PPH). Positive results from any of these ISAs may be used to speed up prosecution in these countries. The EPO is not part of the Global PPH initiative, unlike the USPTO or Korea, and so a positive result from the EPO as ISA is less likely to be usable for PPH in non-IP5 countries.

If the EPO is chosen as ISA, a subsequent European phase application can be prosecuted considerably faster, because searching has already been carried out. If another ISA is chosen, the requirement for the EPO to carry out a supplementary search can delay examination for a year or more.

If you want patents to be granted quickly and you know where you wish to enter the national/regional phase, you can choose the ISA best suited for this.


As can be seen there are a number of factors to consider what selecting the ISA. Key questions to consider in making the decision are: is the applicant willing to pay more money up front to save costs in the long run? Where is the national regional phase likely to be entered? And does the application potentially relate to excluded subject matter or claim multiple inventions? If you would like advice on this, or any other matter, please feel free to contact us.