As a self employed person, are NI deductions tax deductible at the end of year? So, say you earn 10k but pay £300 in voluntary NI over the year, that brings your income down to 9,700 that you have to declare?
No NI deductions are not tax deductable. Note you should be paying Class 2 self employed contributions and not class 3 voluntary contributions. http://www.hmrc.gov.uk/rates/nic.htm