Thank you Frances.

'In 1841 printed forms, called schedules, were issued which had to be given to each head of household in the week prior to census night (a Sunday), collected the following day and then entered into the Census Enumerators Books...since this was in the days of widespread illiteracy it is very likely that the enumerator was responsible for filling in the schedule for many.'

I am looking at census records from 1871 to 1911.

My problem is that quite often the surname was spelt wrong, or in one case the first name of the head was completely wrong, which seems unlikely if the head of the household completed the form.

Also, I have two families, and I am trying to confirm when the heads were born (non UK).

But taking each census date, and the age recorded on the census, gives a different calculated year of birth almost every time, including census records, marriage certificates and death certificates.

It is possible that they didn't know how old they were with any accuracy?