Holders of an Oxford Single Sign On are advised to check in the Commentary section of LexisLibrary, in Westlaw UK's Book collection, and in the IBFD's Research Platform's Books to see if there are relevant titles there. Their holdings may be hard to find in normal SOLO searches.
Remember: The Bodleian Official Papers collection is on the Ground Floor/Level 0 of the St Cross Building. It houses an extensive collection of Westminster thinking & planning on all aspects of tax law in print.
Subject searches to try in SOLO
Taxation -- Philosophy
Taxation Moral and ethical aspects
Taxation -- Law and legislation -- Economic aspects
Fiscal policy -- Moral and ethical aspects;