People of Senghenydd first come into the limelight of history in 1670 when they were taxed by Charles II as part of the Welsh contribution to the running of his royal household and government. The sum needed was £1,200,000 per annum of which most was to be obtained from customs dues, excise dues and other levies. In 1661, the sum was short by £300,000 and an entirely new levy was devised. This consisted of two shillings on all domestic hearths, payable by two equal half-yearly instalments at Michaelmas (29 September) and Lady Day (25 March). Payment was to be made by the occupier, or, if the house was empty, by the owner. The money was to be collected by the petty constables and forwarded together with the names of the defaulters, to the high constables who in turn remitted it to the county sheriffs. The sheriffs were responsible for the safe transmission of the money to the Exchequer in London. People were excempt who were too poor to pay taxes or church and parish rates, and those who, upon certification by parish officers and ministers and approval by the justices of the peace, could be shown to occupy premises worth not more than twenty shillings per annum or to be possessed of real or personal property worth not more than ten pounds.

Charitable institutions such as schools and almshouses endowed with no more than £100 per annum were also exempt as were industrial hearths, i.e. 'any blowing house and stamp, furnace or kiln'. No specific mention was made of smiths' forges or bakers' ovens and this proved a fertile ground for disputes.

Between 1662 and 1689, when the tax was abolished, the Hearth tax had very nearly doubled its net value to the Exchequer. From this episode two apparently complete assesements have survived form the county of Glamorgan of which the 1670 Hearth Tax assesssment has been taken as a window on Glamorgan communities in the mid 17th century.

Parkinson, E. (1994) The Glamorgan Hearth Tax Assessment of 1670, Cardiff: South Wales Record Society