The Scottish census in March 2022 will not be collecting accurate data on sex. Its guidance to answering the What is your sex? question says:
If you are transgender the answer you give can be different from what is on your birth certificate. You do not need a Gender Recognition Certificate (GRC).
If you are non-binary or you are not sure how to answer, you could use the sex registered on your official documents, such as your passport.
A voluntary question about trans status or history will follow if you are aged 16 or over. You can respond as non-binary in that question.
The census is used to inform policy decision making in the areas of sex and health, equality monitoring and education. How can decisions be made on data that is not reliable?
An independent policy analysis collective in Edinburgh, Murray Blackburn Mackenzie, is challenging this, but Scotland's Census has said it won't be making any further changes.
MBM post to their Twitter account @mbmpolicy whenever they have an update and their webpage is murrayblackburnmackenzie.org/sex-and-gender-identity-data-in-the-census/. They also have much to say on the GRA.
There's very little in the Scottish press about this; I have only seen coverage in The Times.
This is a hugely important issue.