Very few legal fields are as tangled and difficult as tax law. That's why you should have a tax attorney on your side if you ever have to step into this particular legal minefield, especially when it comes to audits and anything associated with trusts, wills, or large estates.
Any sizable business should have an expert in tax law on retainer; a tax attorney is preferable, but an accountant may do in some cases. Since it's their duty to remain apprized of any changes in the tax code, you won't have to; plus, they'll be invaluable when tax time rolls around.