diff --git a/flang/lib/Semantics/check-declarations.cpp b/flang/lib/Semantics/check-declarations.cpp
--- a/flang/lib/Semantics/check-declarations.cpp
+++ b/flang/lib/Semantics/check-declarations.cpp
@@ -107,7 +107,8 @@
   void CheckDefinedIoProc(
       const Symbol &, const GenericDetails &, GenericKind::DefinedIo);
   bool CheckDioDummyIsData(const Symbol &, const Symbol *, std::size_t);
-  void CheckDioDummyIsDerived(const Symbol &, const Symbol &);
+  void CheckDioDummyIsDerived(
+      const Symbol &, const Symbol &, GenericKind::DefinedIo ioKind);
   void CheckDioDummyIsDefaultInteger(const Symbol &, const Symbol &);
   void CheckDioDummyIsScalar(const Symbol &, const Symbol &);
   void CheckDioDummyAttrs(const Symbol &, const Symbol &, Attr);
@@ -118,6 +119,13 @@
   void CheckDioVlistArg(const Symbol &, const Symbol *, std::size_t);
   void CheckDioArgCount(
       const Symbol &, GenericKind::DefinedIo ioKind, std::size_t);
+  struct TypeWithDefinedIo {
+    const DerivedTypeSpec *type;
+    GenericKind::DefinedIo ioKind;
+    const Symbol &proc;
+  };
+  void CheckAlreadySeenDefinedIo(
+      const DerivedTypeSpec *, GenericKind::DefinedIo, const Symbol &);
 
   SemanticsContext &context_;
   evaluate::FoldingContext &foldingContext_{context_.foldingContext()};
@@ -132,6 +140,8 @@
       characterizeCache_;
   // Collection of symbols with BIND(C) names
   std::map<std::string, SymbolRef> bindC_;
+  // Derived types that have defined input/output procedures
+  std::vector<TypeWithDefinedIo> seenDefinedIoTypes_;
 };
 
 class DistinguishabilityHelper {
@@ -1742,15 +1752,36 @@
   }
 }
 
+void CheckHelper::CheckAlreadySeenDefinedIo(const DerivedTypeSpec *derivedType,
+    GenericKind::DefinedIo ioKind, const Symbol &proc) {
+  for (TypeWithDefinedIo definedIoType : seenDefinedIoTypes_) {
+    if (*derivedType == *definedIoType.type && ioKind == definedIoType.ioKind &&
+        proc != definedIoType.proc) {
+      SayWithDeclaration(proc, definedIoType.proc.name(),
+          "Derived type '%s' already has defined input/output procedure"
+          " '%s'"_err_en_US,
+          derivedType->name(),
+          parser::ToUpperCaseLetters(GenericKind::EnumToString(ioKind)));
+      return;
+    }
+  }
+  seenDefinedIoTypes_.emplace_back(
+      TypeWithDefinedIo{derivedType, ioKind, proc});
+}
+
 void CheckHelper::CheckDioDummyIsDerived(
-    const Symbol &subp, const Symbol &arg) {
-  if (const DeclTypeSpec * type{arg.GetType()}; type && type->AsDerived()) {
-    return;
+    const Symbol &subp, const Symbol &arg, GenericKind::DefinedIo ioKind) {
+  if (const DeclTypeSpec * type{arg.GetType()}) {
+    const DerivedTypeSpec *derivedType{type->AsDerived()};
+    if (derivedType) {
+      CheckAlreadySeenDefinedIo(derivedType, ioKind, subp);
+    } else {
+      messages_.Say(arg.name(),
+          "Dummy argument '%s' of a defined input/output procedure must have a"
+          " derived type"_err_en_US,
+          arg.name());
+    }
   }
-  messages_.Say(arg.name(),
-      "Dummy argument '%s' of a defined input/output procedure must have a"
-      " derived type"_err_en_US,
-      arg.name());
 }
 
 void CheckHelper::CheckDioDummyIsDefaultInteger(
@@ -1781,7 +1812,7 @@
     const Symbol &subp, const Symbol *arg, GenericKind::DefinedIo ioKind) {
   // Dtv argument looks like: dtv-type-spec, INTENT(INOUT) :: dtv
   if (CheckDioDummyIsData(subp, arg, 0)) {
-    CheckDioDummyIsDerived(subp, *arg);
+    CheckDioDummyIsDerived(subp, *arg, ioKind);
     CheckDioDummyAttrs(subp, *arg,
         ioKind == GenericKind::DefinedIo::ReadFormatted ||
                 ioKind == GenericKind::DefinedIo::ReadUnformatted
diff --git a/flang/lib/Semantics/runtime-type-info.cpp b/flang/lib/Semantics/runtime-type-info.cpp
--- a/flang/lib/Semantics/runtime-type-info.cpp
+++ b/flang/lib/Semantics/runtime-type-info.cpp
@@ -886,12 +886,6 @@
       }
     } else { // user defined derived type I/O
       CHECK(proc->dummyArguments.size() >= 4);
-      bool isArg0Descriptor{
-          !proc->dummyArguments.at(0).CanBePassedViaImplicitInterface()};
-      // N.B. When the user defined I/O subroutine is a type bound procedure,
-      // its first argument is always a descriptor, otherwise, when it was an
-      // interface, it never is.
-      CHECK(!!binding == isArg0Descriptor);
       if (binding) {
         isArgDescriptorSet |= 1;
       }
diff --git a/flang/test/Semantics/io11.f90 b/flang/test/Semantics/io11.f90
--- a/flang/test/Semantics/io11.f90
+++ b/flang/test/Semantics/io11.f90
@@ -364,3 +364,253 @@
     stop 'fail'
   end subroutine
 end module m16
+
+module m17
+  ! Test the same defined input/output procedure specified as a generic
+  type t
+    integer c
+  contains
+    procedure :: formattedReadProc
+  end type
+
+  interface read(formatted)
+    module procedure formattedReadProc
+  end interface
+
+contains
+  subroutine formattedReadProc(dtv,unit,iotype,v_list,iostat,iomsg)
+    class(t),intent(inout) :: dtv
+    integer,intent(in) :: unit
+    character(*),intent(in) :: iotype
+    integer,intent(in) :: v_list(:)
+    integer,intent(out) :: iostat
+    character(*),intent(inout) :: iomsg
+    read(unit,iotype,iostat=iostat,iomsg=iomsg) dtv%c
+    print *,v_list
+  end subroutine
+end module
+
+module m18
+  ! Test the same defined input/output procedure specified as a type-bound 
+  ! procedure and as a generic
+  type t
+    integer c
+  contains
+    procedure :: formattedReadProc
+    generic :: read(formatted) => formattedReadProc
+  end type
+  interface read(formatted)
+    module procedure formattedReadProc
+  end interface
+contains
+  subroutine formattedReadProc(dtv,unit,iotype,v_list,iostat,iomsg)
+    class(t),intent(inout) :: dtv
+    integer,intent(in) :: unit
+    character(*),intent(in) :: iotype
+    integer,intent(in) :: v_list(:)
+    integer,intent(out) :: iostat
+    character(*),intent(inout) :: iomsg
+    read(unit,iotype,iostat=iostat,iomsg=iomsg) dtv%c
+    print *,v_list
+  end subroutine
+end module
+
+module m19
+  ! Test two different defined input/output procedures specified as a 
+  ! type-bound procedure and as a generic for the same derived type
+  type t
+    integer c
+  contains
+    procedure :: unformattedReadProc1
+    generic :: read(unformatted) => unformattedReadProc1
+  end type
+  interface read(unformatted)
+    module procedure unformattedReadProc
+  end interface
+contains
+  subroutine unformattedReadProc1(dtv,unit,iostat,iomsg)
+    class(t),intent(inout) :: dtv
+    integer,intent(in) :: unit
+    integer,intent(out) :: iostat
+    character(*),intent(inout) :: iomsg
+    read(unit,iotype,iostat=iostat,iomsg=iomsg) dtv%c
+    print *,v_list
+  end subroutine
+  !ERROR: Derived type 't' already has defined input/output procedure 'READUNFORMATTED'
+  subroutine unformattedReadProc(dtv,unit,iostat,iomsg)
+    class(t),intent(inout) :: dtv
+    integer,intent(in) :: unit
+    integer,intent(out) :: iostat
+    character(*),intent(inout) :: iomsg
+    read(unit,iotype,iostat=iostat,iomsg=iomsg) dtv%c
+    print *,v_list
+  end subroutine
+end module
+
+module m20
+  ! Test read and write defined input/output procedures specified as a 
+  ! type-bound procedure and as a generic for the same derived type
+  type t
+    integer c
+  contains
+    procedure :: unformattedReadProc
+    generic :: read(unformatted) => unformattedReadProc
+  end type
+  interface read(unformatted)
+    module procedure unformattedReadProc
+  end interface
+  interface write(unformatted)
+    module procedure unformattedWriteProc
+  end interface
+contains
+  subroutine unformattedReadProc(dtv,unit,iostat,iomsg)
+    class(t),intent(inout) :: dtv
+    integer,intent(in) :: unit
+    integer,intent(out) :: iostat
+    character(*),intent(inout) :: iomsg
+    read(unit,iotype,iostat=iostat,iomsg=iomsg) dtv%c
+    print *,v_list
+  end subroutine
+  subroutine unformattedWriteProc(dtv,unit,iostat,iomsg)
+    class(t),intent(in) :: dtv
+    integer,intent(in) :: unit
+    integer,intent(out) :: iostat
+    character(*),intent(inout) :: iomsg
+    write(unit,iotype,iostat=iostat,iomsg=iomsg) dtv%c
+    print *,v_list
+  end subroutine
+end module
+
+module m21
+  ! Test read and write defined input/output procedures specified as a 
+  ! type-bound procedure and as a generic for the same derived type with a
+  ! KIND type parameter where they both have the same value
+  type t(typeParam)
+    integer, kind :: typeParam = 4
+    integer c
+  contains
+    procedure :: unformattedReadProc
+    generic :: read(unformatted) => unformattedReadProc
+  end type
+  interface read(unformatted)
+    module procedure unformattedReadProc1
+  end interface
+contains
+  subroutine unformattedReadProc(dtv,unit,iostat,iomsg)
+    class(t),intent(inout) :: dtv
+    integer,intent(in) :: unit
+    integer,intent(out) :: iostat
+    character(*),intent(inout) :: iomsg
+    read(unit,iotype,iostat=iostat,iomsg=iomsg) dtv%c
+    print *,v_list
+  end subroutine
+  !ERROR: Derived type 't' already has defined input/output procedure 'READUNFORMATTED'
+  subroutine unformattedReadProc1(dtv,unit,iostat,iomsg)
+    class(t(4)),intent(inout) :: dtv
+    integer,intent(in) :: unit
+    integer,intent(out) :: iostat
+    character(*),intent(inout) :: iomsg
+    read(unit,iotype,iostat=iostat,iomsg=iomsg) dtv%c
+    print *,v_list
+  end subroutine
+end module
+
+module m22
+  ! Test read and write defined input/output procedures specified as a 
+  ! type-bound procedure and as a generic for the same derived type with a
+  ! KIND type parameter where they have different values
+  type t(typeParam)
+    integer, kind :: typeParam = 4
+    integer c
+  contains
+    procedure :: unformattedReadProc
+    generic :: read(unformatted) => unformattedReadProc
+  end type
+  interface read(unformatted)
+    module procedure unformattedReadProc1
+  end interface
+contains
+  subroutine unformattedReadProc(dtv,unit,iostat,iomsg)
+    class(t),intent(inout) :: dtv
+    integer,intent(in) :: unit
+    integer,intent(out) :: iostat
+    character(*),intent(inout) :: iomsg
+    read(unit,iotype,iostat=iostat,iomsg=iomsg) dtv%c
+    print *,v_list
+  end subroutine
+  subroutine unformattedReadProc1(dtv,unit,iostat,iomsg)
+    class(t(3)),intent(inout) :: dtv
+    integer,intent(in) :: unit
+    integer,intent(out) :: iostat
+    character(*),intent(inout) :: iomsg
+    read(unit,iotype,iostat=iostat,iomsg=iomsg) dtv%c
+    print *,v_list
+  end subroutine
+end module
+
+module m23
+  type t(typeParam)
+  ! Test read and write defined input/output procedures specified as a 
+  ! type-bound procedure and as a generic for the same derived type with a
+  ! LEN type parameter where they have different values
+    integer, len :: typeParam = 4
+    integer c
+  contains
+    procedure :: unformattedReadProc
+    generic :: read(unformatted) => unformattedReadProc
+  end type
+  interface read(unformatted)
+    module procedure unformattedReadProc1
+  end interface
+contains
+  subroutine unformattedReadProc(dtv,unit,iostat,iomsg)
+    class(t(*)),intent(inout) :: dtv
+    integer,intent(in) :: unit
+    integer,intent(out) :: iostat
+    character(*),intent(inout) :: iomsg
+    read(unit,iotype,iostat=iostat,iomsg=iomsg) dtv%c
+    print *,v_list
+  end subroutine
+  subroutine unformattedReadProc1(dtv,unit,iostat,iomsg)
+    class(t(3)),intent(inout) :: dtv
+    integer,intent(in) :: unit
+    integer,intent(out) :: iostat
+    character(*),intent(inout) :: iomsg
+    read(unit,iotype,iostat=iostat,iomsg=iomsg) dtv%c
+    print *,v_list
+  end subroutine
+end module
+
+module m24
+  ! Test read and write defined input/output procedures specified as a 
+  ! type-bound procedure and as a generic for the same derived type with a
+  ! LEN type parameter where they have the same value
+  type t(typeParam)
+    integer, len :: typeParam = 4
+    integer c
+  contains
+    procedure :: unformattedReadProc
+    generic :: read(unformatted) => unformattedReadProc
+  end type
+  interface read(unformatted)
+    module procedure unformattedReadProc1
+  end interface
+contains
+  subroutine unformattedReadProc(dtv,unit,iostat,iomsg)
+    class(t(*)),intent(inout) :: dtv
+    integer,intent(in) :: unit
+    integer,intent(out) :: iostat
+    character(*),intent(inout) :: iomsg
+    read(unit,iotype,iostat=iostat,iomsg=iomsg) dtv%c
+    print *,v_list
+  end subroutine
+  !ERROR: Derived type 't' already has defined input/output procedure 'READUNFORMATTED'
+  subroutine unformattedReadProc1(dtv,unit,iostat,iomsg)
+    class(t(*)),intent(inout) :: dtv
+    integer,intent(in) :: unit
+    integer,intent(out) :: iostat
+    character(*),intent(inout) :: iomsg
+    read(unit,iotype,iostat=iostat,iomsg=iomsg) dtv%c
+    print *,v_list
+  end subroutine
+end module