I don't know if this information has been posted at RootsChat or not but in case it hasn't, here is a list of census data that is missing according to ScotlandsPeople:
Missing Census Data
The following list details the Census Data (RD number and name) missing for each year and the reason why.
1881
821 Dumfries, Dumfriesshire (Ed's 13-27) 822 Dunscore, Dumfriesshire
1851
We regret that the following Registration Districts are unavailable at the present time. Every effort is being made to rectify this:
Angus
277, Careston
278, Cortachy & Clova
279, Coupar Angus
280, Craig
281, Dun
Ayrshire
597, Kilmarnock
Kincardineshire
268, Strachan
Caithness
We are aware of some issues with the Caithness registration districts of Bower, Canisbay, Dunnet and Halkirk.
1841
93, Cromdale, Moray, entries can be found under Inverallan
167, Seafield, Banffshire , book has no entries
324, Aberfeldy, Perthshire , book has no entries
367, Kinloch Rannoch, Perthshire , book has no entries
400, Abdie, Fifeshire , book has no entries
406, Auchtermuchty, Fifeshire , book has no entries
409, Balmerino, Fifeshire , book has no entries
415, Ceres, Fifeshire , no book
416, Collesie, Fifeshire , no book
418, Creich, Fifeshire , no book
419, Cults, Fifeshire , no book
420, Cupar, Fifeshire , no book
421, Dairsie, Fifeshire , no book
423, Dunbog, Fifeshire , no book
439, Kinghorn, Fifeshire , book has no entries
440, Kinglasie, Fifeshire , book has no entries
442, Kirkcaldy, Fifeshire , book has no entries
444, Leslie, Fifeshire , book has no entries
509, Cumlodden, Argyllshire , book has no entries
535, Tarbert, Argyllshire , book has no entries
556, Lochranza, Buteshire , book has no entries
557, North Bute, Buteshire , book has no entries
577, Auchinleck, Ayshire , book has no entries
776, Kirkhope, Selkirkshire , book has no entries
809, Teviothead, Roxburghshire , book has no entries
862, Corsock Bridge, Kirkcudbrightshire , book has no entries
864, Dalbeattie, Kirkcudbrightshire , book has no entries