Hi, Mary. i have wrestled with this, too. right now we don't use them - we just look up by name - but we are considering a move to eBooks with Overdrive and that would require a unique number for each patron. depending on how large your church is, just the birth month and date might cause problems with duplicates. is there is any restriction on format with the software? maybe you could use something like the first couple letters of the last name along with the birth month and date. or some other number or letter combination that would reduce the likelihood of duplicates. in our case, i would only assign one for people who wanted to use the eBooks, thinking it would be too time consuming to go do all of them when not everyone would use the service. if it is required for any check outs at all in your system i think i would do a combination of the two (ie. commit to a format, assign the PIN to patrons as they come in to check something out, and then on workdays or when time permits assign PINS to remaining patrons and then notify them. over time they will all get done. Good luck!