Due to the frequency of threatened partial government shutdowns caused by agency funding lapses–and the occasional actual shutdown, most recently in 2013–policies regarding pay and benefits are well established and presumably would continue unchanged.
Employees who are ordered to continue working are guaranteed to be paid for that time since the government has incurred an obligation to them. For employees furloughed, there is no such assurance. In past shutdowns they have been paid as well, but that requires action by Congress each time. That issue most likely would be addressed in whatever measure eventually passes to restore funding.
The mechanics of exactly when employees would be paid for the shutdown time depends on the length of the closing and payroll cycles, also an uncertainty at present. A relatively brief shutdown–most have been only a few days–could start and end within a pay period and there might be no practical impact.
FEHB coverage continues during a shutdown, with the employee share to be paid retroactively later if an employee’s pay for a pay period would not be large enough to cover it. Premiums under FEDVIP and FLTCIP insurance similarly would accumulate but if a shutdown went on for a number of weeks, those programs would directly bill enrollees. FEGLI insurance continues without cost to the employee.
There would be no impact on an employee’s eventual retirement benefit unless an employee was on unpaid leave for more than six months in a calendar year–an impossibility at this point except for employees who were on unpaid status for three months or more earlier in the year.