Reading this post just now

Originally posted by DaveB View Post
A Subject Access Request is Free after the 25th and they have 30 days to respond. You can then check what they hold and point out any corrections and request they be put right. Again they 30 days to do this.

However, if the HMRC website lets you check all the personal data they hold on you they they will just point you to that as it allows you to check and correct details at any time.
After tomorrow, it might be interesting (and possibly helpful to other contractors) to see the data that HMRC holds about you, particularly in regards to the investigation.