Gift Tax Extension Form Returned to Sender

Early in 2025, my husband and I gifted a condo worth about $250,000 to our daughter and son-in-law. Even though we will never come close to the $10 million threshold for estate and gift taxes unless we win the lottery, we knew we’d each have to file a Form 709 for gift taxes. Of course, the tax now is 0.

I file the taxes in the household, so I filed automatic extensions for each of us on April 10th. I sent the two forms certified, in separate envelopes. I would get around and file the actual Forms 709 sometime in the summer.

Today, a month after the due date, I received my husband’s extension form back unopened. Stating “Return to Sender. Not deliverable as addressed. Unable to forward.”

I sent it to the correct address. However, it appears the zip code was blocked by a post office bar code.

I’m freaking out. Any form is already late. I won’t have time to complete the form until summer. But it’s my husband. He will probably insist on my completing it tonight.

What should I do? Can I file in the summer and attach the envelope stating we tried to file timely and it was returned through no fault of our own?

As always, many thanks.