Rent shortfall

Possession - Section 8 and Section 21

Hi

I have a tenant who for some months now has been underpaying the rent since he had a work accident and was therefore rendered unable to work and in receipt of universal credit/disability allowance.

He's renting a 3 bedroom house however housing benefit are currently only paying him a rent allowance equivalent to a single bedroom not the full rent.

I agreed to this arrangement as a goodwill temporary measure since he's overall been a good long-term tenant who has fallen on hard times and due to the pandemic however I feel this has gone on too long and the time for him to pay the full previous rent is long overdue or alternatively he should look elsewhere for accommodation. I'm also not convinced he's genuinely claiming disability benefit and suspect he's actually working but not passing on the full rent.

I'd prefer to approach the subject delicately to avoid an adverse reaction on his part hence I was wondering what might be the best approach and what are some of the pitfalls to be aware of given his circumstances and the temporary ban on evictions. I would be prepared to work with him in an amicable way to support him being re-housed if required.

For example would a section 21 notice be the best route? and if so what documentation would I need to have in order to avoid any roadblocks along the way.