Definition:

What is a Safe Harbor?
A safe harbor is a provision in a law or regulation that affords protection from liability or penalty under specific situations or if certain conditions are met. (Business Dictionary.com). Sometimes a safe harbor reduces liability if "good faith" is demonstrated.

Some examples of tax safe harbor provisions
This definition isn't very helpful, so here are some examples of tax safe harbor provisions:

• Section 530 of the Internal Revenue Code (IRC) includes a safe harbor provision relating to classification of workers as independent contractors. Under this provision, a company is not liable for employment taxes if it can demonstrate a reasonable basis for treating workers as independent contractors and if the employer can meet all of three reasonable basis standards. To arts and crafts professions, this safe harbor helps artists who are independent contractors.
  
• In another example, the new Health Care Law (the "Affordable Care Act") includes a safe harbor for affordability for employee health care coverage.
  
• Another safe harbor provision is the IRS Special Accounting Rule that allows employers to treat non-cash fringe benefits provided in November or December as being provided in the following year.