Taxes
Two numbers, and neither is advice. The safe harbor is what to pay so the IRS cannot charge a penalty however the year turns out. The other is what a dollar of business spending is actually worth, which is the reason photographing a receipt is worth the ten seconds.
This year, for the rate
Only ever used to find which bracket the next dollar falls in. Neither figure is reported anywhere or put in the export.
Counted in the income that picks your bracket, and left out of the QBI deduction, which the IRS excludes wages from by name. What counts as reasonable compensation is between you and your CPA. Estreat does not have a view on it.
Last year, for the safe harbor
Both off last year's 1040. Total tax is line 24 and AGI is line 11.
Withholding, which counts against it
Federal income tax expected to come out of a paycheck this year, yours or a spouse's on a joint return. The IRS treats it as paid evenly across the four due dates, so it comes straight off what the instalments have to carry. Leave it blank if nobody on the return is on payroll.