What is it?
The CSA stands for clinical skills assessment. It is the practical exam you need to pass to finish your GPST years and get your certificate of completion of training (CCT), and MRCGP after your name!

The RCGP have described the aim of the exam:

"The aim of the CSA is to test a doctor’s ability to gather information and apply learned understanding of disease processes and person-centred care appropriately in a standardised context, make evidence-based decisions, and communicate effectively with patients and colleagues. Being able to integrate these skills effectively is a key element of this assessment" 

http://www.rcgp.org.uk/gp-training-and-exams/mrcgp-exam-overview/mrcgp-clinical-skills-assessment-csa.aspx

the format
The CSA involves 13 cases. Each lasting 10 minutes. You will get 2 minutes between each case. You will get your own room, just like in 'real life' and the patients come to you. After 7 cases you will get a short break, in which you can leave your room and go out for a cup of tea / get some biscuits. The break is 15 minutes in length. During this time you can also peruse the upcoming cases.

When can I take it?
The Royal College of GP's Keeps an updated version of the CSA dates and deadlines for applications on their website. Click here to access it

Your room
As mentioned above, you will get your own room for the duration of the exam. Within your room is a large locker where you can keep your belongings.

In addition to what you bring down to the CSA, you will also find additional 'equipment' in your room. Possibilities include pregnancy charts, peak flow charts etc.. Please bear in mind that the additional equipment may not be required for your upcoming cases. In fact you may not get any cases that need any of the additional equipment provided. Therefore, don't try to guess your cases based on what is on your table.

The iPad.. as this is a source of much anxiety for candidates - I have created a specific section for it below.

The ipad
The RCGP has gone with the times, and is therefore using iPads to display all of the information you will need for your cases.

I shall try to allay the anxieties and fears by stating that the iPad was really VERY easy to use. Before you start the exam, you will get a brief presentation that instructs you how to use the iPad. When you enter the room you will find the iPad in a stand on  your desk. Before using the iPad you will first have to log in using your GMC number. After this is completed, all the 'doctor' information for your 13 cases will be visible to you. You can, if you wish, go through all the cases in advance. During the exam, any additional information, such as exam findings, can be released by the examiner. You will be instructed in your induction how to access the additional information.  

If you want a further in-depth read on how to use the iPads, then please click here where you will find the official RCGP document relating to the iPad in reference to the exam. Please note that the document also contains an image of the iPad as it will look during your exam. 

it costs how much?!
Taken from the RCGP website (October 2018):
For AiTs who registered with the College before 1 July 2015: £1685
For AiTs who registered with the College after 1 July 2015 : £1325
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Following a re-alignment of fees for AiTs announced in June 2015, those who joined the College as AiTs after 1 July 2015 are paying a higher annual subscription than previous cohorts, and will therefore pay a lower rate for their AKT and CSA examinations. 
It is not all doom and gloom however - there is some good news. You may be able to claim the cost of the exams back against income tax. For further information on the topic I have linked the official RCGP advice (for which you will need your RCGP login details) and also a draft letter that can help you claim from HM Revenue and Customs (HMRC):

Please click here for further information (you will require your RCGP username and password)
Please click here to download the example letter to write to the HMRC

If you do decide to claim, then you will need to send the above letter as well as proof that you passed the exam - your pass certificate is sufficient.  You will also need proof of payment - click here for this (again RCGP online login details required to access). Lastly, many trainees were asked for a copy of their contract - you should be able to obtain this from your practice, by asking your practice manager nicely!