Spain’s annual consumer-price inflation was estimated at 4.9% in September 2026, six tenths of a percentage point above August, according to the flash estimate published by the National Statistics Institute (INE) on 29 September. The CPI also rose 0.3% from August in the preliminary monthly comparison. These are estimates pending the full release, not the final September index. The distinction matters because the flash reading is intended to provide an early signal and may change when complete information is incorporated.

The measure excluding unprocessed food and energy, which INE calls underlying inflation, was estimated to rise 3.1% annually, up two tenths from the previous month. The harmonised index of consumer prices (HICP), designed to support comparison between countries, was estimated at 5.0% year on year and 0.6% month on month. CPI and HICP are related but not identical measures. Their coverage and methods differ, so the 4.9% national CPI should not be substituted for the 5.0% harmonised estimate when making cross-country comparisons.

INE attributed the September annual CPI movement partly to fuels and lubricants for personal vehicles: prices were rising in September 2026, whereas they had fallen in September 2025. Package-holiday prices also declined less than they had a year earlier. The release describes these influences as shaping the comparison, not as a complete decomposition of every price change. It does not say that all households face the same inflation rate, nor that a particular fuel or holiday price alone accounts for the six-tenths rise.

An annual inflation rate compares the index level with the same month a year earlier; it is not the percentage change in a household’s total bill since August. The monthly CPI estimate of 0.3% answers the nearer-term comparison, while the 4.9% rate summarizes the twelve-month change. Both are rounded headline measures. A household’s own costs can differ because its purchases, location, contract timing and eligibility for public support do not match the national index basket exactly.

The flash estimate is the early stage of INE’s continuous monthly CPI operation. Its methodological description lists a 2025 base period and weights based on the previous year. The index uses price collection across 177 municipalities, 487 traditionally collected items and 263 scanner-data items, with approximately 200,000 monthly prices from traditional collection. INE describes the general method as a Laspeyres chain index and says collection uses visits to outlets, email, telephone, internet and scanner data. The breadth improves coverage but does not make every individual price directly observable in the headline.

Underlying inflation is a defined special aggregate, not a measure of all prices stripped of every temporary influence. In this release it excludes unprocessed food and energy products. Its 3.1% annual rate therefore offers a different view of the basket from the overall CPI, which includes those categories. The overall and underlying indicators can move at different speeds. Neither one by itself identifies the cost pressures faced by a particular household or predicts how prices will develop in later months.

INE said the figures released on 29 September were a preview of final September data to be published the following month. A flash estimate is provisional by design; users should preserve that status in headlines, comparisons and any downstream calculations. If the final value changes, the final publication will supersede this estimate for a settled historical observation. Until then, the 4.9%, 3.1% and 5.0% figures should be cited as the respective flash estimates for CPI, underlying inflation and HICP.

The useful conclusion is that the flash CPI points to faster annual price growth in September, while the monthly rate remained a separate, smaller comparison and the underlying measure stayed below the headline. The release supplies a timely national indicator rather than a cost-of-living account for every person. Readers comparing countries should use harmonised measures and matched periods; readers assessing purchasing power need income and household-specific spending evidence as well. The final INE release and later monthly observations are required to see whether the estimate is confirmed and whether the acceleration persists.