Fence designs support a certain amount of stress. You can get the most strength out of your fence by anchoring the buried part of the fence posts with concrete. Unfortunately, these anchors make the job of moving a fence post later a bit of a task. Moving a vinyl fence post anchored with concrete means removing the concrete anchor as a whole while avoiding damage to the vinyl post.
Dig up the fence post along with its concrete anchor with your shovel. Remove all of the soil around the base. Lift the fence post and its concrete anchor with the help of at least one assistant.
Dig a new hole in whatever location you desire. Make the hole 6 inches deeper and 12 inches wider than the concrete anchor on your fence post. Place a 4-inch layer of sand into the bottom of the hole.
Lower the concrete anchor on your post into the new hole with the help of your assistants. Hold the level to each side of the vinyl post and adjust it to make it perfectly plumb, or vertical.
Fill the hole with concrete mix and water. Check the plumb of the post and adjust it as necessary. Add as much concrete as will fit in the hole around, and over the old concrete anchor. Leave the post alone. Let the concrete cure for 72 hours so the new concrete is dry and bonded to the old concrete anchor.