Learn about forming and registering your business online, and how to complete other types of business filings. Register your business (opens in a new tab).An Allegheny Health Network purchase order number must appear on all invoices. Any invoice received without a purchase order number may be returned. Include all necessary proof: documents, forms and schedules for your exemptions (if applicable), simply filling in the dollar amount is not adequate. A guide for businesses needing straightforward answers to Pennsylvania Sales and Use Tax questions and audit guidance. For assistance in completing this form, please call the Real Estate Division at (412) 255-2300 or come to the Real Estate Division in-person. •. The taxes that small business owners do pay in Pennsylvania depend on factors like your business structure, employer status, industry, and business activities. When completing these steps, it's important to be accurate and thorough. Sales tax rate lookup and sales tax item calculator.