I do not keep statistics on this but some of my clients use this method, against my advice. I am not sure what you are asking in your final question as I don't think the client's methods can vary from the recordkeeper (TPA). I know that many TPAs want to use the method outlined in the IRM as administratively it is much more convenient (and some try to force its use). We let the clients know that even if a plan sponsor decides to use the IRM method, the IRS reserves the right to ask for the hardship source docs. The information letter on which the IRM is based notes that the auditor should only ask for the source documents in 2 circumstances, but those circumstances are not included in the IRM and even if they were they are only guidance to an auditor. If audited and the participant doesn't have the source documents or cannot find them, seems like the employer may have to go into Audit CAP (luckily none of my clients have had this issue under audit). Convenience = increased audit risk.