The first Tredyffrin tax returns in existence are from 1715. In the first returns only the rating information is given, but as the century progressed the tax returns became more complex. The summary information from each 18th century tax return is provided in the downloadable Excel spreadsheet. Tax information covering the whole of Chester County (but not for every year) is available at the following Chester County Archives Web Page
The 1798 Glass tax returns are available through the 1798 Map.
When land was purchased from the Proprietors of Pennsylvania there was an annual charge, a quit rent. This was usually set at 1 shilling sterling per 100 acres per year. Quit rents first appeared in feudal times when payment released the land owner from various feudal duties. After the Revolution the State of Pennsylvania paid a large sum of money to the heirs of William Penn to compensate them for the loss of the quit-rents, which were then abolished. The following web page tabulates the Quit Rents.
Information on the tax and census returns has been obtained from the Chester County Archives and Chester County Historical Society. The Quit Rent information is from the Pennsylvania State Archives.