@MichaelMcDonald we have not worked with PSG as they essentially compete with us. When Sage sells an HRMS deal direct, these are the folks who do the consulting work. I guess what I am saying is @DougHiggs, bingo, they compete with their re-seller community for work.
PSG is asking for the Perpetual Check History file to get check details. I suspect they will reconcile the detail with the summary buckets maintained in the Payroll module. This way they can ensure they have the MTD, QTD, and YTD buckets balanced by employee. They also need the info so the system can properly balance ACA reporting at end if the year.
Regarding @JeffSchwenk question regarding if they know how to pull the data, I'm sure their SOW called for the client to populate spreadsheet templates which PSG provides for loading balances and history. We provide the same starting point for our fixed fee SOW's. We also offer additional services to assist with extracting and transforming their data for import as well but these are additional services beyond a standard SOW. Look on the bright side, at least your getting SOME professional services out of the transition from the customer.