Seligman on Income Tax

A copy of ERA Seligman's The income tax : a study of the history, theory and practice of income taxation at home and abroad is available here at the time of writing.

Stafford Northcote (1842-61 budgets)

Stafford H. Northcote, Twenty years of financial policy: a summary of the chief financial measures passed between 1842 and 1861, with a table of budgets.

Essentially the first in the British Budgets series, written by a future Chancellor of the Exchequer.  Some interesting and balanced comments about the Irish crisis from a financial perspective.

Income Tax Acts (1799-1952)

The older UK Income Tax Acts are not that easy to find online, but these links work as at the date of posting.  No joy on 1918 yet.

Income Tax Act 1799
Income Tax Act 1803 (at p. 1012)
Income Tax Act 1842
Income Tax Act 1952