We too have had several clients receive these letters and here is what i discovered.  Most are due to the IRS recalculating the penalty.  When reviewing the Info worksheet for the client Part VIII "Direct Deposit & Refund Disbursement Options" has "No bank selected" for "Selected Processor" 

If you select for electronic funds withdrawal for the balance due then you cannot have direct deposit also.

I found and i quote "The IRS generally stopped issuing paper refund checks to individual taxpayers after Sept. 30, 2025. " This was due to "The Executive Order 14247:  Modernizing Payments To and From America's Bank Account"  The IRS is moving to all electronic payments to and from them.

Most clients are receiving a second letter that gives details on the change.  We are advising clients to wait and let the IRS mail them a check because most elderly clients anyway have too much trouble with technology to set up an account.