The Institute of Leadership is one of the professional bodies and learned societies, approved by HM Revenue & Customs (HMRC) for the purposes of Section 344 ITEPA 2003 (formerly S201 ICTA 1988).
This means you are able to claim tax relief on the cost of maintaining your Institute membership; whether employed or self-employed.
In order to claim relief you need to contact HMRC. In most cases this relief will be accommodated by way of an additional allowance in your PAYE code, used by your employer when calculating your monthly pay.
If you are self-employed and complete an annual Self Assessment Tax Return, then you need to include a claim for relief in relation to your professional fees and subscriptions.