The short version
For supported present-interest gifts, the annual exclusion is subtracted per donee. For 2025 gifts, the IRS instructions say the annual exclusion is $19,000 per donee. A $23,000 cash gift to one donee can therefore create a $4,000 taxable gift before lifetime credit.
The form then computes tentative gift tax and applies available credit. In many simple cases, that can leave zero estimated current gift tax due, while still using part of the lifetime gift and estate tax exclusion.
Why the screen may show tentative tax
The tentative tax line is not a bill by itself. It is an intermediate step before credit. Tax Paperwork shows it because hiding the line makes the final zero look unexplained.
Where the public preview stops
The Form 709 preview is for narrow no-current-tax-due cases. If prior taxable gifts, DSUE, restored exclusion, gift splitting, GST, nonresident facts, or a current payment may apply, get independent CPA, EA, or attorney review before filing.