When it comes to scanning, the resolution is not a matter. On the other hand, tax documents, even a 200-pixel per-inch scan might offer you great enough quality for other targets. 300 PPI is nearly enough, and it is tough to seek a scanner at this moment that can assist less than 600 PPI. Similarly, if you do not plan to crop in the tiny part of the image, or print the image at a huge size than the original, 600 PPI is better.
Other types of originals, however, request high resolution. If you are scanning 35mm slides, for instance, you will perhaps need to print them at a larger size than the original, which proves you will scan them at a high resolution. If you need to realize the specific information in the original, such as the stamp; you will scan it at a high resolution. In other circumstances, you might need the scanner which claims an optical resolution of a minimum of 4800 PPI.