Can a lender change their mind after closing on my purchase after 5 months due to a tax lien issue?

that seems very odd, however you need to seek legal advise directly

If the loan hasn't closed, then yes!!.. But once your loan is closed, then the only way they can is if you committed loan fraud.. meaning you knew you had the tax lien, but you said "No" on Residential Loan Application, section VIII, item f. it asks if you are delinquent on any federal debt.. if you marked "No" when you knew you had the lien, then that's loan fraud, and the lender can call the note due. I'm a Broker here in Scottsdale AZ and I only lend in Arizona. If you or someone you know is looking for financing options, feel free to contact me or pass along my information. 480-287-5714 WilliamAcres.com