CPI + 1% is in the rent standard policy statement as the normal default limit on social sector rent increases, but for this year it has been varied to 7% for general needs properties. See paras 1.9 to 1.12 here: https://www.gov.uk/government/publications/direction-on-the-rent-standard-from-1-april-2020/policy-statement-on-rents-for-social-housing
