You have received some excellent information from the other attorneys.
I would like to emphasize an indirect point made by some of the other attorneys: trademark rights are limited based on jurisdiction. In other words, if you own a trademark in the United States, that gives you rights only in the United States. It does not give you rights in any other country/jurisdiction. If you want rights in other countries/jurisdictions, you need to actively do something, namely, file a trademark application there. So the 6 month priority filing date given under the Paris Convention will only apply if you actually file an application in the United Kingdom claiming Paris Convention priority (usually this requires a copy of your U.S. application upon which the priority filing is based). If you do not file an application in any other country within that 6 month time frame and claim Paris Convention priority, that priority is lost forever. You can file an application in other countries/jurisdictions at any time, you will simply not have the benefit of the Paris Convention priority filing date.
I strongly urge you to consult with an experienced trademark attorney who can review all of the specific facts of your situation and devise a foreign filing strategy that meets the needs of your business and is within your budget.
Best of luck!
This answer is for general information purposes only. This communication does not constitute legal advice, nor does it form an attorney-client relationship.
To some extent this is a question of UK law, so unless there is a UK lawyer on Avvo you may not get a fully satisfactory answer.
If you file an application to register your trademark in the UK within 6 months of filing in the U.S. (and claim priority to your U.S. application), your priority date, or "effective filing date" will be the filing date of your U.S. application. So you would win against someone who filed before you in the UK, but after your U.S. application was filed.
If you do not file a UK application within 6 months, you will lose any rights in the UK to your U.S. application, so your UK application would rely on whatever date you file it in the UK.
However, in your question you specify that you start selling in the UK. In the U.S., using a trademark in commerce gives you rights even if you do not file a trademark application, and you could oppose any later trademark application by another on that basis. I do not know if that is the law in the UK as well. But you would only be entitled to your first use date in the UK, not your first use or filing date in the U.S., if you are going to rely on prior use.
Your question is a little confusing.
The registration is valid as long as you timely file all post registration maintenance documents. For a trademark registration to remain valid, an Affidavit of Use (Section 8 Affidavit) must be filed: (1) between the fifth and sixth year following registration, and (2) within the year before the end of every ten-year period after the date of registration. The registrant may file the Section 8 Affidavit within a grace period of six months after the end of the sixth or every tenth year, with payment of an additional fee. The registrant must also file a Section 9 renewal application (Section 9 Renewal) within the year before the end of each successive 10-year period following the date of registration, or within a grace period of six months thereafter, with payment of an additional fee. Assuming the Section 8 Affidavit and Section 9 Renewal are timely-filed as indicated above, the registration will be renewed for a 10-year term. If the Section 8 Affidavit and Section 9 Renewal are not timely filed, the registration will be cancelled. Registrations cancelled due to the failure to file a Section 8 Affidavit and Section 9 Renewal cannot be revived or reinstated.
I hope this helps.
Attorney at Law
Disclaimer: This is a general discussion of legal principles by a California lawyer and does not create an attorney/client relationship. This is not intended to be legal advice in your specific case. It's impossible to give detailed, accurate advice based on a few sentences on a website. You should always seek advice from an attorney licensed in your jurisdiction who can give you an informed opinion after reviewing all of the relevant information in your case.
You misunderstand the 6 month priority under the Paris Convention. It runs from your application date, not your registration date. There is NO 6 month priority period starting from your date of registration. Since US applications take longer than 6 months to register, if you have not filed well before US registration, you are too late. Mistakes like that are why do-it-yourself trademark work is poor business practice. An experienced trademark attorney would not make that mistake (at least not more than once, and that is why you want an "experienced" attorney - so the mistakes have already been made and the lessons already learned.)
However, there is a right of opposition against a UK trademark application or an EC (OHIM) application based on "relative grounds", namely conflict with prior common law rights or prior registrations. See http://www.out-law.com/page-9662 You may have some hope of success based on your prior sales in the UK in such an opposition. That is very fact specific, and would require the assistance of UK counsel. A US trademark attorney with more than a year or two of experience will likely have a UK associate to consult. Another reason you don't DIY but instead hire an experienced attorney - for the contacts they have to save time and money.
There is another consideration here. If you are doing international sales, you should be taking advantage of the Madrid Protocol to file a so called "international application". You don't even mention it, suggesting you are a novice who should, as I have said twice above, be using experienced trademark counsel and, in view of your question, you know that is NOT YOU.
You came here for free advice, and that shows you are smart enough to know that you don't know enough to do this without help. The advice is DON'T DO THIS, get a trademark attorney (since you are in Illinois, one in Illinois would be best - since I am one, what do expect me to say, right? - but it is true.) so it is done right. You may already be too late, so do it without delay. I suspect you also need a business attorney, as a business attorney would likely have seen that you got proper advice and you would not need to ask the question.
So far, this is free to you. Until you pay a fee, I am not your lawyer and you are not my client, so you take any free advice at your sole risk. I am licensed in IL, MO, TX and am a Reg. Pat. Atty. so advice in any other jurisdiction is general advice and should be confirmed with an attorney licensed in that jurisdiction.
Hi Maximiliano, You again, welcome.
Just one note FYI. In the USA you must use your mark BEFORE you can register it, In your Argentina, and most of the world, you register your mark BEFORE you use it,
USPTO Registered Patent Attorney, Master of Intellectual Property law, MBA I am neither your attorney, nor my answers or comments in AVVO.com create an attorney-client relationship with you. You may accept or disregard my free advice in AVVO.com at your own risk. I am a Patent Attorney, admitted to the USPTO and to the Florida Bar.