In addition the following building yards received building orders for Type XXI boats by telex on 6.7.43:
| Deutsche Werft AG Hamburg | 24 boats |
| Danziger Werft AG | 12 boats |
| F. Schichau GmbH Danzig | 18 boats |
| Deschimag AG Weser Bremen | 24 boats |
| Lübecker Flender-Werke AG | 12 boats |
| Kriegsmarinewerft Wilhelmshaven | 12 boats. |
These orders were subsequently canceled on 30.9.43 before the arrival of written confirmation and the assignment of official U-numbers.
Coastal U-boat type of advanced design with Walter propulsion system developed in 1943
| Surface/submerged displacement: | 155/≈170 t |
| Overall length/beam/draught: | 27.10 m/3.00 m/4.20 m |
| Standard main armament: | 3 torpedo tubes (2 bow, 1 stern) with 3 torpedoes |