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Please note that the IRS can levy any bank account that your husband is the owner, or part owner of. Even though they have not yet mentioned his personal bank account (Account B), this does not mean that they won't get around to issuing a levy on it. A person normally has 21 days to release the levy or stop it as the bank will hold funds for 21 days before releasing them to the IRS.
If your husband is not a joint owner of the accounts with you and your sons, there shouldn't be an issue with them levying those accounts. However, you are dealing with the IRS. They have been known to make errors in this arena. Your thought of going to the bank to discuss this matter is probably a good idea to make sure that no errors are made if the levy is not stopped. Remember, your husband has 21 days to try to stop the levy. Paying the balance due or setting up an installment agreement (payment plan) may stop the levy. He can call the IRS at 1-800-829-1040 and they can direct him on how to set up the payment plan. Depending upon how much he owes in back taxes, financials may or may not be required when setting up the payment plan.
Regarding the house...
Under a tenancy by the entirety, creditors of an individual spouse may NOT attach and sell the interest of a debtor spouse. Only creditors of the couple may attach and sell the interest in the property owned by tenancy by the entirety. I hope this clarifies matters for you.