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  • Make proofreading patents a priority

Photonics Spectra
Nov 2008
Amanda D. Francoeur,

So you’ve gone through the grueling patent application process of hiring a lawyer, compiling the required data, filing your application, waiting several months for the US Patent and Trademark Office to evaluate it, and now you’ve finally been issued a patent. Did you forget anything?

Not proofreading is one of the most common and unfortunate oversights that applicants make. Failure to make a careful final check may lead to a trying and time-consuming procedure to correct the patent and could affect its enforceability and require substantial financial outlay to rectify the error.

Typical errors include typographical and grammatical mistakes within the description and claims sections of an application. Although minor, they could cause drastic misinterpretation of the operation or the scope of protection of an invention.


Mistakes are not always the applicant’s fault. They can be made in the US Patent and Trademark Office records after the patent has been filed, so it is especially important to proofread a second time, after the patent has been issued.

Considering that a patent can be more than 100 pages long, it is helpful to know that there are services to help you proofread. Companies such as Computer Patent Annuities Ltd. and Clairvolex Knowledge Processes Ltd. are especially useful, given that they are experienced intellectual property service providers.

Found an error?

If you find errors in your issued patent, you can apply for a certificate of correction.

In August of this year, the US Patent and Trademark Office issued more than 2800 certificates of correction out of the 13,885 patents filed. About 15 percent of all patents issued require a certificate of correction, which totals about 25,000 certificates each year.

For a certificate to be approved for correction, errors must be clerical, typographical or minor. Changes in a patent can neither constitute new matter nor require re-examination, and inaccuracies must be obvious to a person skilled in the subject.

In the application for a certificate of correction, a written request (cover letter) is required with the signature of the owner of the record, along with the patent and application numbers, the names of all inventors included on the issued patent, the date the patent was issued, the title of the invention and facts supporting the intended correction.

Next is the required PTO/SB/44 form (also referred to as PTO-1050). The form should contain the same information as the cover letter and should include the page and line numbers of the error or errors and the correct information to replace it. A copy of the filed patent should be attached with the specified errors highlighted. In cases where the error is the applicant’s, a $100 fee is required.

The completed form should be mailed to the patent commissioner at the certificate of correction branch: P.O. Box 1450, Alexandria, VA 22313-1450.

If a certificate of correction is rejected, a transmittal letter can be sent to the correction branch indicating an appeal, which should list any discrepancies and concerns regarding denial of the certificate. On approval of a certificate of correction, no changes will be made to the actual patent filed with the US Patent and Trademark Office. Instead, the certificate of correction will be attached to the original document.

From osmolarity to osmolality

Although errors can appear to be minor, some have the potential to completely change the product described in the patent. In the example of Central Admixture Pharmacy Services (CAPS) v. Advanced Cardiac Solutions (ACS), a certificate of correction approval of a spelling change turned out to be much more complex than changing an “r” to an “l.”

CAPS, a provider of intravenous prescriptions, was issued a patent for a solution that’s used during heart surgery. Afterward, the company filed for a certificate of correction to replace within the original patent application’s claims section all instances of the word “osmolarity” (amount per liter) with the word “osmolality” (amount per kilogram). The disputed word describes the amount of a certain chemical required in the solution. The correction was granted on the basis that the mistake was minor and would be evident to a person skilled in the same field.

After the certificate of correction was issued, CAPS sued ACS for infringement, but ACS countered by challenging the certificate of correction, asserting that the correction had broadened the original claim because it produced a less concentrated solution compared with the original one and because the error would not have been evident to a trained person. The court sided with ACS and nullified the certificate of correction it had granted CAPS, and CAPS dropped the infringement claim.

In the event that a more important error in the claims portion of a patent must be corrected, an inventor can file to have his patent reissued. This requires that a claim be either too broad or too narrow to be protected by the original patent. However, when correcting an error, the filer cannot introduce new subject matter, as the claims must apply to the same invention described in the original patent. All reissue applications must be filed less than two years after the original patent was issued.

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