BobKamman
Level 15

From the only reference to Letter 417C in the Manual, it seems to me that it applies to refund claims (which are unlikely for an 1120-S).  Someone at IRS might have been trying to pound a square peg into a round hole, because there is no standard form letter for requesting the original return when an amended 1120-S is involved.  Are you sure that the original 2019 return did not inadvertently have the "amended" box checked?  

TC 150 - Original Return Not Obtained
  1. If a TC 150 is located and there is no reason to request the original return for verification, make the adjustment using the appropriate blocking series. See IRM 21.5.2.4.22, Blocking Series (BS).

    If the original return is requested but not received andThen
    The return is charged out to another areaContact the area for the return or a complete copy.
    The return is not charged out to another areaRequest the return a second time.
    A second request does not secure the return
    1. If unable to secure the return after the two previous requests, input another request as "Special Search" using Form 2275, Records Request, Charge and Recharge. For information on where to fax Form 2275, refer to Who/Where Tab, then click on the Files Contact Listing (the former IAP) to research the fax number of the file location needed.

    2. Send a Letter 418C, Amended/Original Return Unavailable; Copy Requested, to the taxpayer.
      Note: Exhaust all in-house means to secure the return before contacting the taxpayer.

    3. Suspend the case for 40 days; 70 days for overseas taxpayers that meet international criteria. Refer to IRM 21.8.1.2.14, International Forms Processing, for additional information.

    4. If no reply to the Letter 418C, Amended/Original Return Unavailable; Copy Requested, follow procedures in IRM 21.5.3, General Claims Procedures.