Some partnerships may may still have not received their UTR and so will not be able to file their tax returns on time.
Under self-assessment a partnership will not be able to avoid a late filing penalty by making payment of tax on time.
A lack of a UTR will count as a reasonable excuse for failing to file a return on time, and anyone affected should download this form: 'Unable to file using SA online - claim for reasonable excuse'
HMRC's guidance is here .