What's the difference between regular and supplemental runs?

This table describes how regular and supplemental payroll runs calculate federal taxes, based on the default settings.

What wages are being processed	Process and pay with other?	Taxation Type input value	For this tax	Uses this calculation method for regular runs	Uses this calculation method for supplemental runs
Regular only	Yes		Federal income tax (FIT)	Annualized	N/A
	Yes		State income tax (SIT)	Default state regular	N/A
	No		FIT	Annualized	N/A
	No		SIT	Default state regular	N/A
Supplemental only	No	N/A	FIT	Tiered Flat Rate Note: You can override this at the payroll statutory unit (PSU) and tax reporting unit (TRU) levels.	Tiered Flat Rate Note: You can override this at the PSU and TRU levels.
	No	N/A	SIT	Default state supplemental Note: You can override this at the PSU and TRU levels if the state supports alternate methods.	Default state supplemental Note: You can override this at the PSU and TRU levels if the state supports alternate methods.
	Yes	N/A You defined the elements before the input value was introduced.	FIT	Concurrent Aggregation	Tiered Flat Rate
	Yes	N/A You defined the elements before the input value was introduced.	SIT	Uses Concurrent Aggregation If not applicable for the work or residence state, uses default state supplemental	Default state supplemental Note: You can override this at the PSU and TRU levels if the state supports alternate methods.
	Yes	Regular	FIT	Concurrent Aggregation	Tiered Flat Rate
	Yes	Regular	SIT	Uses Concurrent Aggregation If not applicable for the work or residence state, uses default state supplemental	Default state supplemental Note: You can override this at the PSU and TRU levels if the state supports alternate methods.
	Yes	Supplemental	FIT	Tiered Flat Rate Note: You can override this at the PSU and TRU levels.	Tiered Flat Rate Note: You can override this at the PSU and TRU levels.
	Yes	Supplemental	SIT	Default state supplemental Note: You can override this at the PSU and TRU levels.	Default state supplemental Note: You can override this at the PSU and TRU levels.
Regular and supplemental	Yes	Regular	FIT	Concurrent Aggregation	Tiered Flat Rate for supplemental wages Note: You can override this at the PSU and TRU levels. Ignores regular wages
	Yes	Regular	SIT	Uses Concurrent Aggregation If not applicable for the work or residence state, uses default state calculation method	Default state supplemental Note: You can override this at the PSU and TRU levels. Ignores regular wages
	Yes	Supplemental	FIT	Tiered Flat Rate Combined Note: You can override this at the PSU and TRU levels.	Tiered Flat Rate for supplemental wages Note: You can override this at the PSU and TRU levels. Ignores regular wages
	Yes	Supplemental	SIT	Default state method for regular and supplemental Note: You can override this at the PSU and TRU levels if the state supports alternate methods.	Tiered Flat Rate for supplemental wages Note: You can override this at the PSU and TRU levels. Ignores regular wages