Mailing of the Polestar-printed job started today (7 March) with delivery complete by Census Day on 27 March.
The Census pack comprises a 32pp questionnaire complete with leaflets and posted in a personalised envelope.
Paul Tolhurst, director of field operations at Royal Mail, said: "This is one of the single biggest postings Royal Mail will have dealt with and we are confident we can rise to the challenges it presents.
"Our people will be working hard over the coming weeks to deliver the 26 million Census forms."
Printing of the 30m questionnaires took Polestar 71 days while the leaflets alone took 48 days to produce. Adding in 198 days of envelope printing, the giant print run weighed in at 5,200 tonnes of paper.
Tim Smith, managing director of Polestar, said: "Even for us, the scale is a little daunting, but it is also very exciting to get down to the level of engineering detail that we have managed in order to give the reliability and quality of the product."
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