A brief demonstration with examples by Candice Foers-Bates
Parallax is often caused when using a wide angle lens.
Try moving away from the subject and zooming in.
Want to get rid of any remaining parallax? Bring in guides to help you. Select the whole image. Go to ‘Edit’ > ‘Transform’ > ‘Skew’
Skew the image until you’re happy, then you’ll need to crop it.
The finished, ‘straightened’ building.
To recap… The subject taken on a wide angle lens from a relatively close position. The subject taken on a standard lens from a more distant point. The subject skewed in PhotoShop