Enter a follow-up material

What causes this issue?

You have set the discontinuation indicator, but not specified a
follow-up material.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

With this discontinuation indicator (simple/parallel discontinuation),
you must enter a follow-up material since the material to be
discontinued will be replaced in materials planning on the date
specified with the follow-up material entered here.
Even if you want to specify a follow-up material in the bill of
material (BOM), you must define a follow-up material here. A follow-up
material specified in the BOM has a higher priority than one specified
in the material master record.

Error message extract from SAP system. Copyright SAP SE.