Census returns for England and Wales are held at The National Archives (TNA) in Kew.

TNA has millions of records which are each classified and contain a unique reference.
The above reference is followed by a Registration District Number

The above reference is followed by a Registration District Number

One of the most important things to know about censuses, are the ways that they are referenced. Knowing the right reference for a census page lets you go straight to that page.

But censuses are not referenced by book and page numbers.

The references are by Piece and Folio, for example 2422/25, 
or more accurately, RG9 2422/25 as the RG9 tells us that it is the 1861 census.

• A census Piece is a collection of many individual enumerators' books for a district.
• A census Folio is a sheet within one of those books
  (note: not a "page" - a folio is the front and back of a sheet, in other words, two pages)

Each enumerator had a pre-printed book that he had to fill in. A book may have anything from about 20 sheets up to about 40 (double sided). Those books were collected, and were later bound into combined books of between about 50 and 200 leaves. It is this combined book that is a census Piece.

After binding, the books had the folio number stamped on the upper right corner of every sheet. (The back of the sheet was not stamped). This stamped number is the Folio number.

Above: the stamped Folio number (12)

Note that the page number (21) is irrelevant now. It is the page number of that enumerator's individual book, and since his book will have been combined into a larger volume along with lots of other books, there will be many pages bearing the page number 21 ! So we don't use page numbers when stating a census reference!

So far so good.... folio 12 as shown above is the sheet of paper in the book. The folio number refers to both sides of that sheet, (originally pages 21 & 22).

Now, there is a problem that creeps in. When the pages were stamped with a folio number, then the person doing it often lost concentration. Therefore he often missed stamping a sheet, or stamped two consecutive sheets with the same number.

Therefore we can have some folio references that apply to four pages (or more) instead of two! It was a mistake.

When (if) the mistake was spotted, then the folio numbers were "fudged", as, for example 11a and 11b

Which illustrates our point nicely. In this case:

• original book pages 17 &18 are Folio  11a
• original book pages 19 and 20 are Folio 11b
• and original book pages 21 and 22 are Folio 12

Summary: When stating a census reference always use the RG number (which identifies the year), followed by the census Piece number, followed by the census Folio number.

e.g. RG9 764/12 (in that format)

For the 1911 census the references changed slightly – all that is needed to refer to a census entry for 1911 is the Department or Series Code RG14, followed by the RD number (up to five digits) and the SN (Schedule Number).