The maps and schedules held by the commissioners passed to the [[Inland Revenue]] (the predecessors of [[HMRC]]) and are now held in the [[The National Archives]] at [[Kew]]<ref>Foot, p.20</ref> (classes IR29 and IR30). Most of the extant parish copies are now held at the county record office. The diocesan copies for most Welsh parishes are held in the [[National Library of Wales]] at [[Aberystwyth]]. Prior to the publication of large scale [[Ordnance Survey]] maps in the late 19th century, tithe maps were frequently copied (in whole or part) for other purposes: for example in connection with planned railways, or as part of the title deeds transferred on a sale of land. More recently, tithe maps and apportionments have often been used for reference by genealogists and other historical researchers. For many parishes they provide the only large scale map showing the landscape prior to the [[Industrial Revolution]],<ref>Harley, p.35</ref> and they frequently provide the earliest evidence for the [[field system]] in the parish.
