The BAcC home page section marked Research has a sub-heading 'fact sheets' in which you can find an assessment of the value of acupuncture for treating stress in general and anxiety as one of its most common manifestations.
Factsheet on stress is viewable here
Factsheet on anxiety is viewable here
Acupuncture used to be very widely regarded as no more than a technique for reducing stress and pain, but opinion was sharply divided between those who thought the benefits were largely non-specific - being given time and attention, being listened to, lying down relaxing for half an hour - as much as the needles themselves. This is still the case now, and the words 'placebo effect' are used somewhat disparagingly about apparent successes of acupuncture. As one of the senior medical acupuncturists in the UK said, however, if both acupuncture and the 'sham' acupuncture used in a major trial outperform conventional treatment, that has got to be worth investigating.
Stress is such a wide-ranging and inclusive term that it is very difficult to give a blanket answer. In most cases we advise people to seek advice locally and in person for their specific needs, except in those cases where we are sure that acupuncture will not help or may even be contra-indicated, but in this case that is the only answer we can give. How stress presents in your life and what the main presenting causes are can have a huge bearing on how well it can be treated. If someone is trapped in a job they hate with an unpleasant boss whom they have to put up with to pay a large mortgage, there is nothing that treatment can do to change the material circumstances and possibly the best it can manage is to reduce the impact of these day to day vexations. Where the causes are more internal it may be possible to achieve more. Speaking directly to one of our members is the best course of action.