NO - because the instructions are to fill it in on 21st March! If somebody, by any chance, is 'away from home on 21st March' (for whatever reason - ie hospital, prison) then you will have given false information. That would result in somebody being counted TWICE, as all institutions (hospitals, prisons, hostels etc) will be doing them on the correct day.
I do a lot of Genealogy and I LOVE it when previous Censuses are released for public knowledge.
In the past I've found a female ancestor in Prison aged 19 in 1851 and another ancestor in a Workhouse aged 50 in 1901. I am now looking forward to when 'The Next Chapter' is released for 1921 - which will probably be sometime next year!