If you're planning to sell books directly to consumers, you'll also have to obtain tax numbers from your government. (selfpublishingadventure.com)
There are a few different types of tax numbers that individuals might need to utilize when filing their taxes, and it can be confusing to distinguish one from the other. (etfbase.com)
Lastly, you mentioned wanting to hit an after tax number monthly. (biggerpockets.com)