Disclaimer: The materials provided below are informational and should not be relied upon as legal advice.
The IRS will show satisfaction of the lien once it is paid off. I do not believe the IRS will update the amount of the lien based on partial payments. Be sure to consult your own attorney to protect your legal rights.
They will not update the lien. The Lien will stay there until it's paid off, or until they need to re-file it. (or other circumstance such as a discharge) If a pay-off balance is requested, you will receive an accurate pay-off balance through the date indicated, and use that to show anyone that you do not owe $50,000
The lien is filed for the whole amount due at the time of filing the lien. The credit reporting agency can be asked to update the account to show in addition to the lien the amount currently owed on the account. The lien itself will stay on the record as originally filed with no change in the amount of the lien.