I pay for Parker because the updates have value and it is inexpensive, but I never rely upon it for source info. I have found material mistakes in Parker's IRC and regs. At first, I thought I just found an unusual misreference in the Regs. It took me a while to figure out what was going on. Then it happened again. Then I was researching in 213 and knew a provision had been changed by the CARES Act. I had to dig through the act, find the language, compare to 213 as shown, because I really could not believe my eyes. It was quite significant. I emailed Parker, and the response I received was along the lines of, thanks for letting us know, we will go through the CARES Act again with a fine tooth comb. I emailed back and asked what in the world is going on, this is the 3rd time a solo like me has found mistakes in their data, and CARES Act had passed a year ago. They did not respond.
So beware.
I'll search Parker to get some background on an issue, but I always go here when I need to be sure that what I am looking at is accurate.
https://www.taxnotes.com/research/federal