In 1538, Thomas, Lord Cromwell, decreed that every parish in England and Wales should have a book and a coffer with two locks. Each Sunday, the parish parson was to record the baptisms, marriages, and burials that occurred during the week preceding week. There are a few isolated instances of parish registers for dates prior to this, but although the events may have occurred earlier, they were not recorded until 1538 or after. If this procedure was not followed, a fine of s3 p4 was to be paid and used for repairs to the church.
In 1547 the fines were directed to the care of the poor. In 1559 this was changed so that the fines would go half to repairs and half to the poor. A major change was implemented in 1597, when copies of the records were to be sent to each Bishop. Unfortunately, many of the clergy were not diligent in copying and sending their records, and not all dioceses were diligent in maintaining the records. For those areas where they were maintained, however, the records provide an excellent supplement to parish registers, or replacements where the originals may have been damaged or lost.
The Church of England was the official church. Although Non-Conformist congregations started in the sixteenth century, records of these churches usually don’t start until the seventeenth century.
Many parish registers were transcribed and published in the nineteenth and twentieth centuries. These published works are available on many websites, including Google Books and Internet Archive. Try searching for the the name of the parish and the word records to see if your parish of interest is available there.
In addition to these records, images of original records are also available online. Ancestry.com has teamed with the London Metropolitan Archives to put registers from London parishes online.
Many parish registers, both published and original, were indexed by FamilySearch (Community Indexed) and entered into the International Genealogical Index (IGI). Many individuals also contributed information that they had found (Community contribute) These records are searchable on the FamilySearch website. Because the indexed records are known to come from the originals, they are considered quite reliable (although like all secondary sources they should be examined in the original). Because the contributed records can come from anywhere (including “family tradition”) and they do not list a source, they are considered much less reliable and should be used only as clues to find original records. The batch numbers for indexed records are known and available on RootsWeb. Through the RootsWeb interface, you can limit your search to a single parish (although the in theory the same could be accomplished through the search tools on the FamilySearch website).
Besides the IGI, FamilySearch is scanning their microfilms of parish registers and making them available online. Records from 17 counties are currently available.
In 1908 Arthur Meredith Burke published his Key to the Ancient Parish Register of England and Wales. The beginning section of the book includes a history of parish registers in these areas, such as an attempt by Parliament to create a register of church books in each diocese that was defeated by the clergy. It also includes examples of records one might find in the registers. The second part is an annoted index to the registers, with information on each parish and when the earliest surviving records are for that parish. The book is available for download for free from Google Books and the Internet Archive.