After filing an US application how much time should the applicant wait to file a PCT application?
What are the benefits of filing early or late?
Ideal time is to file application is within 12 months from priority. Early filing sometimes speeds up examination.
Benefits of filing late (that is, at the 12 month date)
Benefits of filing early (that is, substantially before the 12 month date)
However, I should note that this benefit of filing early is more theoretical than anything else. Because the sole reason to file a PCT application is to defer when you need to make a decision about subsequent countries (or to defer the costs of those countries). Thus if you are looking to file a PCT application, you are not going to be in any particular hurry to proceed to grant. Thus the value in getting an ISR early is negligible.
One year is the maximum time permitted under the rules.
If your desire is to increase the market value of your patent application, you should file PCT as fast as possible.
If possible file PCT first and US later.
The reason for this is that for most US patent applications no action starts until about two years are passed so their is no way to asses their market value.
In contrast PCT gives you an opinion on the patentability of various claims within six to nine months of the filling.
The PCT report, being independent and treated with respect in most countries, will allow you to market the patent with a greater confidence.