From the PA tax website:
"If you received your income unevenly and you did not make equal payments throughout the year, you may have to claim your safe harbor by completing a REV-1630."
https://revenue-pa.custhelp.com/app/answers/detail/a_id/392
And see this previous TT answer:
Where can I find my rev 1630 form? (intuit.com)
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
