The law changed in April 2014 with regard to National Insurance
From 6 April 2014, Supporting Artiste earnings are treated as self-employed income and will be subject to Class 2 or Class 4 National Insurance. You no longer have a Class 1 National Insurance deduction from your payment and you will receive all payments without National Insurance deductions. You will be responsible for paying Class 2 National Insurance and where applicable Class 4 National Insurance which will be payable along with your self-assessment income tax. This applies to all payments made to you after 6 April 2014.
Please read THIS article that outlines the changes and what you need to do.
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