diff --git a/src/LIB/SURCOUCHE/src/mode_io_write_nc4.f90 b/src/LIB/SURCOUCHE/src/mode_io_write_nc4.f90
index cbde62c6aa205cf01372fe46dd72416779671f4d..238b603567a3d855ed2a043d74ca74fc28f45dfa 100644
--- a/src/LIB/SURCOUCHE/src/mode_io_write_nc4.f90
+++ b/src/LIB/SURCOUCHE/src/mode_io_write_nc4.f90
@@ -35,6 +35,7 @@
 !  P. Wautelet 14/12/2023: add lossy compression for output files
 !  P. Wautelet 15/02/2024: IO_Coordvar_write_nc4: add time dimension for Lagrangian trajectories
 !  P. Wautelet 20/03/2024: add boxes for output files
+!  P. Wautelet 02/10/2024: add netCDF attributes for subfiles
 !-----------------------------------------------------------------
 #ifdef MNH_IOCDF4
 module mode_io_write_nc4
@@ -2871,6 +2872,24 @@ IF (TPFILE%LMASTER)  THEN
   END IF
   IF ( ISTATUS /= NF90_NOERR ) CALL IO_Err_handle_nc4( istatus, 'IO_FILE_WRITE_HEADER', 'NF90_PUT_ATT', 'MNH_COMPRESS_LOSSY' )
 
+  ! Number of subfiles (0 if no subfiles or if is a subfile)
+  ISTATUS = NF90_PUT_ATT( TPFILE%NNCID, NF90_GLOBAL, 'MNH_NSUBFILES', TPFILE%NSUBFILES_IOZ  )
+  IF ( ISTATUS /= NF90_NOERR ) CALL IO_Err_handle_nc4( istatus, 'IO_FILE_WRITE_HEADER', 'NF90_PUT_ATT', 'MNH_NSUBFILES' )
+
+  ! Is this file a subfile
+  IF ( ASSOCIATED( TPFILE%TMAINFILE ) ) THEN
+    ISTATUS = NF90_PUT_ATT( TPFILE%NNCID, NF90_GLOBAL, 'MNH_IS_ROOTFILE', '0' )
+  ELSE
+    ISTATUS = NF90_PUT_ATT( TPFILE%NNCID, NF90_GLOBAL, 'MNH_IS_ROOTFILE', '1' )
+  END IF
+  IF ( ISTATUS /= NF90_NOERR ) CALL IO_Err_handle_nc4( istatus, 'IO_FILE_WRITE_HEADER', 'NF90_PUT_ATT', 'MNH_IS_SUBFILE' )
+
+  ! For the moment, there is only this type: Zsplit
+  IF ( TPFILE%NSUBFILES_IOZ > 0 .OR. ASSOCIATED( TPFILE%TMAINFILE ) ) THEN
+    ISTATUS = NF90_PUT_ATT( TPFILE%NNCID, NF90_GLOBAL, 'MNH_SUBFILE_TYPE', 'Zsplit' )
+    IF ( ISTATUS /= NF90_NOERR ) CALL IO_Err_handle_nc4( istatus, 'IO_FILE_WRITE_HEADER', 'NF90_PUT_ATT', 'MNH_SUBFILE_TYPE' )
+  END IF
+
 !title
 
   !history