Any statement after a STOP RUN or GOBACK is unreachable and therefore dead code which should be removed.
Noncompliant code example
PARAGRAPH1.
  MOVE A TO B.
  STOP RUN.
  MOVE B TO C.
or
PARAGRAPH1.
  MOVE A TO B.
  GOBACK.
  MOVE B TO C.
Compliant solution
PARAGRAPH1.
  MOVE A TO B.
  MOVE B TO C.
  STOP RUN.
or
PARAGRAPH1.
  MOVE A TO B.
  MOVE B TO C.
  GOBACK.