[javi_garcia18]

Hola malaga01, lo que puedes hacer es darle tu una longitud con el write y asi respetaria los espacios en blanco, te pongo un ejemplo:

DATA: v_record(500) TYPE c.
DATA: BEGIN OF t_download OCCURS 0,
linea(500) TYPE c,
END OF t_download.
-------------------------------------------------------------
LOOP AT t_data_comp WHERE lifnr EQ t_reg_pago-lifnr.
WRITE t_data_comp-espacio_blank TO v_record+0(1).
WRITE t_data_comp-tipo_reg TO v_record+1(1).
WRITE t_data_comp-tipo_prod TO v_record+2(1).
WRITE t_data_comp-nro_cuen_abo TO v_record+3(20).
WRITE t_data_comp-razsoc TO v_record+23(40).
WRITE t_data_comp-moneda TO v_record+63(2).
WRITE t_data_comp-impte TO v_record+65(15).
WRITE t_data_comp-tip_doc_id TO v_record+80(3).
WRITE t_data_comp-nro_doc_id TO v_record+83(12).
WRITE t_data_comp-tip_doc TO v_record+95(1).
WRITE t_data_comp-nro_doc TO v_record+96(10).
WRITE t_data_comp-tip_abo TO v_record+106(1).
WRITE t_data_comp-ref_adi TO v_record+107(40).
WRITE t_data_comp-flag_not_abo TO v_record+147(1).
WRITE t_data_comp-flag_del TO v_record+148(1).
WRITE t_data_comp-flag_val_ruc TO v_record+149(1).
WRITE t_data_comp-direccion TO v_record+150(40).
WRITE t_data_comp-distrito TO v_record+190(20).
WRITE t_data_comp-provincia TO v_record+210(20).
WRITE t_data_comp-departamento TO v_record+230(20).
WRITE t_data_comp-contacto TO v_record+250(40).
t_download-linea = v_record.
APPEND t_download.
CLEAR t_download.
ENDLOOP.

IF t_download[] IS NOT INITIAL.
PERFORM zf_donwload_tabla.
ENDIF.

*&---------------------------------------------------------------------*
*& Form zf_donwload_tabla
*&---------------------------------------------------------------------*
* text
*----------------------------------------------------------------------*
* --> p1 text
* <-- p2 text
*----------------------------------------------------------------------*
FORM zf_donwload_tabla .

*Activamos la opción de permitir espacios en blanco.
PERFORM set_trail_blanks(saplgrap) USING 'X'.

CONCATENATE p_file '.txt'
INTO v_file_name.

CALL FUNCTION 'WS_DOWNLOAD'
EXPORTING
filename = v_file_name
filetype = 'ASC'
TABLES
data_tab = t_download
EXCEPTIONS
file_open_error = 1
file_write_error = 2
invalid_filesize = 3
invalid_type = 4
no_batch = 5
unknown_error = 6
invalid_table_width = 7
gui_refuse_filetransfer = 8
customer_error = 9
OTHERS = 10.

ENDFORM. " zf_donwload_tabla

espero que te sirva.. saludos!!!