TaxAct Professional Editions require a unique Preparer Tax Identification Number (PTIN) for each preparer to be entered and verified in Master Information. This is due to strict IRS requirements to prevent tax fraud, as stated on the IRS Frequently Asked Questions: Do I Need a PTIN? webpage, under General Guidance #4: "Can multiple individuals or one office share one PTIN?

"No, every individual who, for compensation, prepares or assists in the preparation of a tax return or claim for refund must have his or her own PTIN and each tax return preparer may only obtain one PTIN."