Client loses job: can underpayment still be coded?

Client ( within SA ) has a liability on lettings income for 2011/12. Being under £3k, I asked for it to be coded.

Client has lost job in the 2012/13 year and has no other codable sources.

They've issued a demand for the tax for 2011/12 and of POA will now be due.

I was slightly surprised they'd picked up so quickly that there is no longer an employment.

But naturally the client is looking for another job.

Can the 2010/11 be deferred on the basis that the client could quite easily have an employment by 6 April 2013, thus enabling the collection by coding adjustment?