Can I freeze macarons and fill them the day of serving?

Shells freeze just fine in my opinion....just make sure they're wrapped well and frozen while still wrapped. Macaron (or any baked good for that matter) will get soggy from the humidity in the air if left to thaw out in the open.

Me again! I just remembered that our local grocery chain sells an assorted selection of macarons in the freezer section as well.

I made green tea macarons, filled with lemon icing and they froze perfectly. Just took out a few as I needed them.

They do not freeze well, whether filled or unfilled. I wouldn't do it. You can store them unfilled in an air-tight container (tin) to fill freshly before serving.