21 CFR §801.45

1. (a)In general. A device that must bear a unique device identifier (UDI) on its label must also bear a permanent marking providing the UDI on the device itself if the device is intended to be used more than once and intended to be reprocessed before each use.
2. (b)UDI for direct marking. The UDI provided through a direct marking on a device may be:
   1. (1)Identical to the UDI that appears on the label of the device, or
   2. (2)A different UDI used to distinguish the unpackaged device from any device package containing the device.
3. (c)Form of a UDI when provided as a direct marking. When a device must bear a UDI as a direct marking, the UDI may be provided through either or both of the following:
   1. (1)Easily readable plain-text;
   2. (2)Automatic identification and data capture (AIDC) technology, or any alternative technology, that will provide the UDI of the device on demand.
4. (d)Exceptions. The requirement of paragraph (a) of this section shall not apply to any device that meets any of the following criteria:
   1. (1)Any type of direct marking would interfere with the safety or effectiveness of the device;
   2. (2)The device cannot be directly marked because it is not technologically feasible;
   3. (3)The device is a single-use device and is subjected to additional processing and manufacturing for the purpose of an additional single use.
   4. (4)The device has been previously marked under paragraph (a) of this section.
5. (e)Exception to be noted in design history file. A labeler that decides to make use of an exception under paragraph (d of this section) must document the basis of that decision in the design history file required by § 820.30(j) of this chapter.