Section 6325(a) of the Internal Revenue Code directs us to release a Federal tax lien within 30 days of when the liability is fully paid or becomes legally unenforceable or the IRS accepts a bond for payment of the liability. ... If we have not released the lien within 30 days, you can ask for a certificate of release.
Publication 1450 - IRS.gov
https://www.irs.gov/pub/irs-pdf/p1450.pdf
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