This is what my accountant advised.
The requirement for filing under MTD is from April onwards. For us, the last period under the old scheme is Jan-Mar. I was advised that I should file in the usual way for the March quarter and then register for MTD only when the direct debit payment has been taken (we pay by HMRC's DD payment function and it appears that registration for MTD might interfere with the payment - I'm not sure about other payment methods).
You could still try filing as per my instructions in my previous post.
