Update
Sage 100 Payroll 2.18 adds a new folder and program options in Sage 100 Payroll. A Utilities folder has been added and contains Payroll Tax Update and Payroll Tax Update Report.
**This is preliminary and subject to change**
During the Payroll Tax Update, a record is written to table \MAS_System\PR_SPASyncControl.M4T. When the tax update completes, this record is deleted. If the update process is interrupted and the record is not deleted, anyone trying to access functions in Payroll will receive the message, ""A Payroll tax update is in process. Please try again in a few minutes."" It a payroll tax update is not in process, deleting the record in PR_SPQSyncControl.M4T will restore access to payroll functions.
Sage support was contacted, but not much help on this one. I had to install a fresh 2018 with Payroll 2.18 and start looking at tables to trace it down. Sage support new to updated payroll. Unless a feature is really needed, I wouldn't rush to install 2018 with payroll until after February 2018 - a month after W-2s are due. I've done one upgrade and regret is an understatement of how we feel.