Final answer:
CPAs and tax advisors generally include disclaimers in communications with clients to avoid malpractice and comply with Circular 230, disclaimers which signal that the advice provided may not be definitive and guard against misinterpretation.
Step-by-step explanation:
Most CPAs and other tax advisors include some form of blanket disclaimer in the tag line of all their e-mail and other written correspondence sent to clients primarily because of malpractice avoidance. The inclusion of disclaimers is meant to limit liability and provide a clear understanding that the information provided may not cover every aspect of law or be completely tailored to the client's situation. This practice has become quite common as a precautionary measure.
The concept of Circular 230 covered opinions rule relates to the standards for certain tax advice and is another reason for the inclusion of disclaimers. The covered opinions rules require certain standards to be met and disclosures to be made when providing written tax advice. By including disclaimers, CPAs ensure that the recipients are aware that the correspondence should not be considered a "covered opinion" as detailed in Circular 230, and thus they guard against potential legal issues.
Therefore, the reason most CPAs and other tax advisors include disclaimers is not due to the 10-80-10 rules, which is not a common term associated with tax advisory practices, but rather due to malpractice avoidance and the requirements of Circular 230 regarding covered opinions.