[Patent Talk] How to Extend the Term of Your Foreign Patents

The term of a patent is commonly known to be 20 years. More precisely, a patent right arises on the date of registration and lasts until 20 years from the filing date of the patent application. For example, if a patent is registered three years after filing, its effective term is 17 years. Accordingly, the later a patent is registered, the shorter its effective term becomes.

What, then, about the term of foreign patents? In the United States, Europe and other countries, the patent term is likewise 20 years. If a Korean applicant files directly in the United States without first filing in Korea, the patent term will be calculated in the same way as above. However, it is common practice to file a Korean application first and then file foreign patent applications claiming priority within one year.

Under the first-to-file principle, patentability requirements such as novelty and inventive step are examined as of the filing date. However, international treaties provide that, when an application is filed in a second country within one year from the filing date of the patent application in the first country while claiming priority, the reference date for assessing patentability is moved back to the filing date in the first country. Strictly speaking, it is the date for assessing patentability that is moved back, but in practice the effect is similar to moving back the filing date itself, so this is sometimes referred to as the "retroactive effect on the filing date."

Because of this practice, people sometimes mistakenly assume that the term of a foreign patent is counted from the filing date in the first country. In fact, the expiration date of a patent in a foreign country is counted from the date of the formal filing in that country, not from the first-country filing date. Where an application claiming priority is filed directly in an individual country, that filing date is the second-country filing date; where a PCT (Patent Cooperation Treaty) application claiming priority is filed, the PCT filing date is the second-country filing date.

In fact, when I worked as an in-house patent attorney, I once mistakenly reported the expiration dates of a competitor's key patent in major countries as 20 years from its filing date in the United States, the first country. In that case, the PCT application had been filed exactly one year after the U.S. filing date....