Many regulated companies have price controls linked to either or both of RPI, CPI and CPIH. Accurate forecasts of these indices at critical points in the year are important for short term budgeting and planning. In the short term, accurate forecasts of these indices are helped by:

Stable “pipeline” relationships between retail/consumer prices and producer prices and currency exchange rate;
Understanding the drivers of other components of these indices, e.g. housing costs;
Understanding the dynamic trends in the “formula effect” wedges between RPI and CPI methodologies;
Predictable seasonality.