Hi Trevor
The International Genealogical Index (IGI) compiled by the Church of Latter Day Saints (Mormons) mainly consists of 2 types of records.
Extractions are transcriptions taken from actual parish registers and should be fairly accurate with regards to the date. However, incorrect spellings and ommissions mean that you may be convinced someone should be in the records for a particular church there but they're not. They usually have batch numbers starting with C, M or P and the statement 'extracted from the registers' on the record page. You don't find burials listed very often in extracted records.
Submissions are made by patrons of the church and should be treated with caution. They can be completely inaccurate (someone's best guess at worst) of they could be correct, for example where someone has taken the trouble to check out the register and found a missing entry or put in an entry from register that hasn't been transcribed. Batch numbers for these entries are in a completely different format. They usually have the wording 'patron submission' somewhere on the record page.
The Hugh Wallis site is an excellent resource for finding out what registers in which areas have been transcribed
http://freepages.genealogy.rootsweb.ancestry.com/~hughwallis/IGIBatchNumbers.htmHope this helps.
Dawn