CPI+3.9% is the Consumer Price Index (CPI) plus 3.9%. CPI is a measure of the rate of inflation – this is the change in prices for goods and services over time. It is based on household spending in the National Accounts.
A new rate is published every month. We're using the December 2021 figure published in January 2022 - this rate is 5.4% for CPI. This, plus the additional 3.9%, totals a 9.3% increase to your plan.
Moving to new CPI+3.9% terms
If we’ve given you notice in your price rise communication that you’re moving to new terms, you can find the new terms here