When requesting a transcript, you should use the last address on record with the IRS. This is the address on the last return that has been filed and processed.
If you changed your address with the Post Office, this sets up mail forwarding and should allow you to receive IRS correspondence. However, this forwarding stops after a certain period of time. In addition, not every postal service will forward government issued refund checks.
You should update your address with the IRS to ensure you receive any correspondence they may send you. Please refer to the article below for additional guidance.
https://www.irs.gov/taxtopics/tc157.html
