Rent arrears

Rent Arrears

I have a tenants who is struggling to pay the rent due Covid19. He is self employed but cannot meet clients and therefore his earnings have been reduced.
I know Landlords are expected to be flexible but my concern is that when arrears keep increasing it will reach a level that cannot be repaid.
I have asked ( via letting agent )if we can agree a payment plan.
The tenant does make a payment each month but usually about 60% of the rent due and therefore each month the arrears increase.
Has anyone had a smiliar experience. I would like to know if it is sensible to wait until we are fully out of lockdown or should action be taken earlier to avoid the arrears reaching a level that cannot be repaid.