diff --git a/devel/trexio/export_trexio.irp.f b/devel/trexio/export_trexio.irp.f
index e2439c8..0d43a02 100644
--- a/devel/trexio/export_trexio.irp.f
+++ b/devel/trexio/export_trexio.irp.f
@@ -32,11 +32,11 @@ program export_trexio
   call check_success(rc)
 
   ! Electrons
-!  rc = trexio_write_electron_up_num(f, elec_alpha_num)
-!  call check_success(rc)
+  rc = trexio_write_electron_up_num(f, elec_alpha_num)
+  call check_success(rc)
 !
-!  rc = trexio_write_electron_dn_num(f, elec_beta_num)
-!  call check_success(rc)
+  rc = trexio_write_electron_dn_num(f, elec_beta_num)
+  call check_success(rc)
 
   ! Basis
 !  rc = trexio_write_basis_type(f, 'Gaussian')
diff --git a/devel/trexio/trexio_f.f90 b/devel/trexio/trexio_f.f90
index a072766..a69343b 100644
--- a/devel/trexio/trexio_f.f90
+++ b/devel/trexio/trexio_f.f90
@@ -265,6 +265,24 @@ interface
      integer(8), intent(in), value :: trex_file
    end function trexio_has_mo_2e_int_eri
 end interface
+interface
+   integer function trexio_has_electron_up_num (trex_file) bind(C)
+     use, intrinsic :: iso_c_binding
+     integer(8), intent(in), value :: trex_file
+   end function trexio_has_electron_up_num
+end interface
+interface
+   integer function trexio_has_electron_dn_num (trex_file) bind(C)
+     use, intrinsic :: iso_c_binding
+     integer(8), intent(in), value :: trex_file
+   end function trexio_has_electron_dn_num
+end interface
+interface
+   integer function trexio_has_ao_cartesian (trex_file) bind(C)
+     use, intrinsic :: iso_c_binding
+     integer(8), intent(in), value :: trex_file
+   end function trexio_has_ao_cartesian
+end interface
 interface
    integer function trexio_has_nucleus_num (trex_file) bind(C)
      use, intrinsic :: iso_c_binding
@@ -1063,6 +1081,27 @@ interface
      real(8), intent(out) :: dset(*)
    end function trexio_read_mo_2e_int_eri
 end interface
+interface
+   integer function trexio_read_electron_up_num_32 (trex_file, num) bind(C)
+     use, intrinsic :: iso_c_binding
+     integer(8), intent(in), value :: trex_file
+     integer(4), intent(out) :: num
+   end function trexio_read_electron_up_num_32
+end interface
+interface
+   integer function trexio_read_electron_dn_num_32 (trex_file, num) bind(C)
+     use, intrinsic :: iso_c_binding
+     integer(8), intent(in), value :: trex_file
+     integer(4), intent(out) :: num
+   end function trexio_read_electron_dn_num_32
+end interface
+interface
+   integer function trexio_read_ao_cartesian_32 (trex_file, num) bind(C)
+     use, intrinsic :: iso_c_binding
+     integer(8), intent(in), value :: trex_file
+     integer(4), intent(out) :: num
+   end function trexio_read_ao_cartesian_32
+end interface
 interface
    integer function trexio_read_nucleus_num_32 (trex_file, num) bind(C)
      use, intrinsic :: iso_c_binding
@@ -1112,6 +1151,27 @@ interface
      integer(4), intent(out) :: num
    end function trexio_read_mo_num_32
 end interface
+interface
+   integer function trexio_read_electron_up_num_64 (trex_file, num) bind(C)
+     use, intrinsic :: iso_c_binding
+     integer(8), intent(in), value :: trex_file
+     integer(8), intent(out) :: num
+   end function trexio_read_electron_up_num_64
+end interface
+interface
+   integer function trexio_read_electron_dn_num_64 (trex_file, num) bind(C)
+     use, intrinsic :: iso_c_binding
+     integer(8), intent(in), value :: trex_file
+     integer(8), intent(out) :: num
+   end function trexio_read_electron_dn_num_64
+end interface
+interface
+   integer function trexio_read_ao_cartesian_64 (trex_file, num) bind(C)
+     use, intrinsic :: iso_c_binding
+     integer(8), intent(in), value :: trex_file
+     integer(8), intent(out) :: num
+   end function trexio_read_ao_cartesian_64
+end interface
 interface
    integer function trexio_read_nucleus_num_64 (trex_file, num) bind(C)
      use, intrinsic :: iso_c_binding
@@ -1161,6 +1221,27 @@ interface
      integer(8), intent(out) :: num
    end function trexio_read_mo_num_64
 end interface
+interface
+   integer function trexio_read_electron_up_num (trex_file, num) bind(C)
+     use, intrinsic :: iso_c_binding
+     integer(8), intent(in), value :: trex_file
+     integer(4), intent(out) :: num
+   end function trexio_read_electron_up_num
+end interface
+interface
+   integer function trexio_read_electron_dn_num (trex_file, num) bind(C)
+     use, intrinsic :: iso_c_binding
+     integer(8), intent(in), value :: trex_file
+     integer(4), intent(out) :: num
+   end function trexio_read_electron_dn_num
+end interface
+interface
+   integer function trexio_read_ao_cartesian (trex_file, num) bind(C)
+     use, intrinsic :: iso_c_binding
+     integer(8), intent(in), value :: trex_file
+     integer(4), intent(out) :: num
+   end function trexio_read_ao_cartesian
+end interface
 interface
    integer function trexio_read_nucleus_num (trex_file, num) bind(C)
      use, intrinsic :: iso_c_binding
@@ -1966,6 +2047,27 @@ interface
      real(8), intent(in) :: dset(*)
    end function trexio_write_mo_2e_int_eri
 end interface
+interface
+   integer function trexio_write_electron_up_num_32 (trex_file, num) bind(C)
+     use, intrinsic :: iso_c_binding
+     integer(8), intent(in), value :: trex_file
+     integer(4), intent(in), value :: num
+   end function trexio_write_electron_up_num_32
+end interface
+interface
+   integer function trexio_write_electron_dn_num_32 (trex_file, num) bind(C)
+     use, intrinsic :: iso_c_binding
+     integer(8), intent(in), value :: trex_file
+     integer(4), intent(in), value :: num
+   end function trexio_write_electron_dn_num_32
+end interface
+interface
+   integer function trexio_write_ao_cartesian_32 (trex_file, num) bind(C)
+     use, intrinsic :: iso_c_binding
+     integer(8), intent(in), value :: trex_file
+     integer(4), intent(in), value :: num
+   end function trexio_write_ao_cartesian_32
+end interface
 interface
    integer function trexio_write_nucleus_num_32 (trex_file, num) bind(C)
      use, intrinsic :: iso_c_binding
@@ -2015,6 +2117,27 @@ interface
      integer(4), intent(in), value :: num
    end function trexio_write_mo_num_32
 end interface
+interface
+   integer function trexio_write_electron_up_num_64 (trex_file, num) bind(C)
+     use, intrinsic :: iso_c_binding
+     integer(8), intent(in), value :: trex_file
+     integer(8), intent(in), value :: num
+   end function trexio_write_electron_up_num_64
+end interface
+interface
+   integer function trexio_write_electron_dn_num_64 (trex_file, num) bind(C)
+     use, intrinsic :: iso_c_binding
+     integer(8), intent(in), value :: trex_file
+     integer(8), intent(in), value :: num
+   end function trexio_write_electron_dn_num_64
+end interface
+interface
+   integer function trexio_write_ao_cartesian_64 (trex_file, num) bind(C)
+     use, intrinsic :: iso_c_binding
+     integer(8), intent(in), value :: trex_file
+     integer(8), intent(in), value :: num
+   end function trexio_write_ao_cartesian_64
+end interface
 interface
    integer function trexio_write_nucleus_num_64 (trex_file, num) bind(C)
      use, intrinsic :: iso_c_binding
@@ -2064,6 +2187,27 @@ interface
      integer(8), intent(in), value :: num
    end function trexio_write_mo_num_64
 end interface
+interface
+   integer function trexio_write_electron_up_num (trex_file, num) bind(C)
+     use, intrinsic :: iso_c_binding
+     integer(8), intent(in), value :: trex_file
+     integer(4), intent(in), value :: num
+   end function trexio_write_electron_up_num
+end interface
+interface
+   integer function trexio_write_electron_dn_num (trex_file, num) bind(C)
+     use, intrinsic :: iso_c_binding
+     integer(8), intent(in), value :: trex_file
+     integer(4), intent(in), value :: num
+   end function trexio_write_electron_dn_num
+end interface
+interface
+   integer function trexio_write_ao_cartesian (trex_file, num) bind(C)
+     use, intrinsic :: iso_c_binding
+     integer(8), intent(in), value :: trex_file
+     integer(4), intent(in), value :: num
+   end function trexio_write_ao_cartesian
+end interface
 interface
    integer function trexio_write_nucleus_num (trex_file, num) bind(C)
      use, intrinsic :: iso_c_binding