PTINs – https://www.irs.gov/tax-professionals/ptin-requirements-for-tax-return-preparers
PPS – https://www.irs.gov/tax-professionals/practitioner-priority-service
Tax Pro webpage- https://www.irs.gov/for-tax-pros
OPR – https://www.irs.gov/tax-professionals/circular-230-tax-professionals
RPO – https://www.irs.gov/tax-professionals/return-preparer-office-rpo-at-a-glance