Hi again.There is no hard and fast rule about a self-employed individual having to have at least two customers to be treated as self-employed but it is a very good idea to do so. If you are working for only one client, HMRC may say that you are really employed and that will be a problem for your "employer" as it could leave them facing backdated PAYE liabilities if if it takes HMRC a while to catch up with them. If the training service have advised you that you need more than one client, that advice will be based on their experience and the possible reluctance of potential clients to take on an individual who has no other clients.You will need to register as self-employed with HMRC which you can do here. The tax year runs from 6 April to 5 April and I'd advise you to run your accounts to 5 April to keep things simple. A tax return will be issued to after the end of the tax year. Take a look here and here for information on tax return submission deadlines and how and when you pay your tax and national insurance liabilities.There is information on the types of expenses you can claim here and here.If you work from home, you will be able to claim a proportion of your home expenses depending on whether you have a room used exclusively for business purposes whilst you are working or whether that room is also used for other purposes whilst you are working. Take a look at the notes starting here. You may also find the notes here useful.There is nothing to stop you taking up an agency postion as an employee at the same time as being self-employed. It is possible to be both employed and self-employed at the same time.I hope this helps but let me know if you have any further questions.