A slight twist, realizing it may, or may not, apply to the self employed welder, but good background anyway... ASME IX is a qualification code, NOT a constructing code. Constructing codes ALWAYS take precidence over the qualification code, for example, from ASME B31.3:
328.2.3 Performance Qualification by Others. To avoid duplication of effort, an employer may accept a performance qualification made for another employer, provided that the Inspector specifically approves. Acceptance is limited to qualification on piping using the same or equivalent procedure wherein the essential variables are within the limits in Section IX. The employer shall obtain a copy from the previous employer of the performance qualification test record,showing the name of the employer, name of the welder or welding operator, procedure identification, date of successful qualification, and the date that the individual last used the procedure on pressure piping.
Of course, in order to qualify to ASME B31.3, the Rules of ASME IX are invoked, but the Piping Committee has, perhaps wisely, allowed the employer (who holds all responsibility in these matters) the option of accepting previous qualifications. This same option is also found in some of the other ASME Constructing codes.
By the way, the Common Arc program is a wonderful thing and I really hope it continues catching on!