Be had my pre reg today. When should I register with HMRC?

When your certificate comes through. The you know you are 100% ready to work!

I was giving up a job so registered as self employed once I'd worked my notice, probably had a couple of weeks before I actually 'worked'

Be had my pre reg today. When should I register with HMRC?

No need to wait...just call HMRC and ask for the information.
Once you get your registration you are then ready to go!

Good luck :thumbsup:

If I was to register now am I still aim to claim my expenses from previous?

If I was to register now am I still aim to claim my expenses from previous?

Yes just put in your first week of trading