It's possible to bring existing ISRCs from outside of DistroKid and use them for a DistroKid upload. It is not possible to use UPCs from outside of DistroKid and use them for new uploads, however.

ISRCs

DistroKid has been appointed by the US ISRC Agency to assign ISRCs for tracks. If your recording has not already been assigned an ISRC (either by you or a party acting on your behalf), DistroKid will generate an ISRC for every song you upload. It's free and automatic.

If you instead need to specify your own ISRC, you can do so on the upload form in the Musician Plus or Ultimate plan. You can click "already got an ISRC code?" on the upload form under the "Upload your audio file" section.

If you'd like to purchase your own ISRCs, visit https://www.usisrc.org/

UPCs

There is no way to specify a custom UPC for DistroKid uploads. A unique DistroKid UPC is generated for every upload to DistroKid.

If you want to apply for a UPC issued by GS1 to use for physical distribution outside of DistroKid, please contact your local GS1 office here.