61 Pa. Code § 117.6
The return of income may be made by an agent if the person liable for the making of the return is unable to make it by reason of illness or continuous absence from this Commonwealth for a period of at least 60 days before the date prescribed by law for making the return. A return may also be made by an agent if the taxpayer requests permission, in writing, of the Department, and the Department determines that good cause exists for permitting the return to be so made. However, assistance in the preparation of the return may be rendered under any circumstances. If a return is made by an agent, it shall be accompanied by the power of attorney, except that an agent holding a valid and subsisting general power of attorney authorizing him to represent his principal in making, executing and filing the income return, may submit a certified copy thereof. The agent, as well as the taxpayer, may incur liability for the penalties provided for erroneous, false or fraudulent returns.
61 Pa. Code § 117.6
This section cited in 61 Pa. Code § 117.10 (relating to signing returns and other documents); and 61 Pa. Code § 145.5 (relating to returns by persons other than taxpayer).