Yes, he can file the gift tax return late and should file it.
If he uses up some of the unified credit the tax on the gift tax return will be $0.
There would be no penalty due to no tax.
You might want to seek a professional to file the gift tax return and make sure a copy is kept of it.
If your filing is more than 60 days late (including
an extension), you'll face a minimum additional tax of at least $205 or
100 percent of the tax due, whichever is less. Failure to pay the gift
tax on time will result in a penalty of 0.5 percent month of the amount due, up to a total of 25 percent. ---Which would be $0 with no tax due.
