Certainly DA's appear on your HMRC account, usually with a due date back dated.
I'm pretty sure I've seen APN values on HMRC accounts as well. Perhaps they were APNs paid that appear as a credit? I did think though that I'd seen outstanding APNs (i.e. due but not paid) as well.
I'll take myself off and check.
The core point here though is that if you have had the warning letters and such but no APN, its EXTREMELY UNLIKELY that HMRC has had a change of heart.
It's more likely that the APN was posted but failed to arrive.
Therefore, you should try to check whether HMRC think you have gone past a payment date without you knowing, rather than get a surprise.