It was compulsory to register all births in Ireland from 1864, however, as many of you will know, not all births were registered with the civil authorities.  There are many reasons why a birth was not registered, not least human error. In some cases it may have been beyond the family’s means to pay to have a birth registered. If a birth was registered late, the family were fined, so they may have chosen not to register the birth at all. In some cases when the family missed the three month window in which to have their child’s birth registered, they simply changed the date of birth of the child so that it fell within the legitimate time period. This means that you may find Irish birth records for a child who was baptised in October of one year, but whose date of birth on their birth certificate is March of the following year.