Final answer:
In this case, Mya, the tax preparer, should retain the waivers for a minimum of six years as per ethical guidelines for tax professionals.
Tax preparers are typically required to retain waivers of conflict of interest for at least three years from the date of tax return preparation, although retaining such documents for up to seven years may be advisable due to other potential legal needs.
Step-by-step explanation:
In the situation described, Mya, the tax preparer, faces a potential conflict of interest after Joshua and Donna, previously a married couple, get divorced. They have both chosen to continue working with Mya and signed separate waivers. The Internal Revenue Service (IRS) has specific guidelines on the duration for which tax preparers must retain records, including any waivers of conflicts of interest. Although these guidelines can vary, a typical period for keeping such waivers is at least three years from the date of the tax return preparation. Nevertheless, given the fact that this is a legal matter, it is always good practice for tax professionals to retain documents for longer periods, possibly up to seven years, as other regulations or issues may arise requiring access to those documents.