---
title: "UK consumer price inflation (CPIH, CPI, RPI)"
method: GET
path: "/api/v1/ons/cpi"
tags: ["Statistical Agencies"]
---

# UK consumer price inflation (CPIH, CPI, RPI)

`GET /api/v1/ons/cpi`

UK headline consumer prices from Office for National Statistics. Returns CPIH index (L522) and annual rate (L55O), CPI index (D7BT) and annual rate (D7G7), and RPI index (CHAW). All monthly. CPIH is the ONS primary inflation measure and is published mid-month roughly 18-20 days after the reference month.

## Query parameters

- `limit` integer — Number of most-recent monthly observations per series.

## Response `200`

CPIH, CPI, and RPI monthly observations with CDID, unit, and frequency metadata.

- EnvelopeOnsCpiPayload
  - `data` OnsCpiPayload, required
    - `cpih_index` OnsSeries, required — One curated ONS CDID series, unified shape regardless of parent dataset.
      - `cdid` string, required — ONS time series identifier (stable 4-char code, e.g. 'L55O', 'MGSX').
      - `title` string, nullable — Series title as published by ONS.
      - `unit` string, nullable — Unit of measure (e.g. '%', 'index 2015=100', 'GBP m', 'persons').
      - `frequency` string, required — Canonical frequency returned in `observations` ('monthly', 'quarterly', 'annual').
      - `observations` OnsObservation[], required — Observations at the canonical frequency, ordered oldest to newest.
        - `period` string, required — ISO 8601 start-of-period (YYYY-MM-DD). Months = first day of month, quarters = first day of quarter, years = January 1.
        - `period_label` string, required — Original ONS label, e.g. '2026 FEB', '2025 Q4', '2024', or rolling LFS label '2025 NOV-JAN'.
        - `value` number, nullable — Numeric observation value. Null if upstream reported an empty cell.
        - `frequency` string, required — Frequency of this row: 'monthly', 'quarterly', or 'annual'.
        - `update_date` string, nullable — ONS updateDate for the observation (ISO 8601 UTC).
      - `rollups` object — Optional higher/lower frequency rollups keyed by 'annual', 'quarterly', or 'monthly'.
    - `cpih_annual_rate` OnsSeries, required — One curated ONS CDID series, unified shape regardless of parent dataset.
      - `cdid` string, required — ONS time series identifier (stable 4-char code, e.g. 'L55O', 'MGSX').
      - `title` string, nullable — Series title as published by ONS.
      - `unit` string, nullable — Unit of measure (e.g. '%', 'index 2015=100', 'GBP m', 'persons').
      - `frequency` string, required — Canonical frequency returned in `observations` ('monthly', 'quarterly', 'annual').
      - `observations` OnsObservation[], required — Observations at the canonical frequency, ordered oldest to newest.
        - `period` string, required — ISO 8601 start-of-period (YYYY-MM-DD). Months = first day of month, quarters = first day of quarter, years = January 1.
        - `period_label` string, required — Original ONS label, e.g. '2026 FEB', '2025 Q4', '2024', or rolling LFS label '2025 NOV-JAN'.
        - `value` number, nullable — Numeric observation value. Null if upstream reported an empty cell.
        - `frequency` string, required — Frequency of this row: 'monthly', 'quarterly', or 'annual'.
        - `update_date` string, nullable — ONS updateDate for the observation (ISO 8601 UTC).
      - `rollups` object — Optional higher/lower frequency rollups keyed by 'annual', 'quarterly', or 'monthly'.
    - `cpi_index` OnsSeries, required — One curated ONS CDID series, unified shape regardless of parent dataset.
      - `cdid` string, required — ONS time series identifier (stable 4-char code, e.g. 'L55O', 'MGSX').
      - `title` string, nullable — Series title as published by ONS.
      - `unit` string, nullable — Unit of measure (e.g. '%', 'index 2015=100', 'GBP m', 'persons').
      - `frequency` string, required — Canonical frequency returned in `observations` ('monthly', 'quarterly', 'annual').
      - `observations` OnsObservation[], required — Observations at the canonical frequency, ordered oldest to newest.
        - `period` string, required — ISO 8601 start-of-period (YYYY-MM-DD). Months = first day of month, quarters = first day of quarter, years = January 1.
        - `period_label` string, required — Original ONS label, e.g. '2026 FEB', '2025 Q4', '2024', or rolling LFS label '2025 NOV-JAN'.
        - `value` number, nullable — Numeric observation value. Null if upstream reported an empty cell.
        - `frequency` string, required — Frequency of this row: 'monthly', 'quarterly', or 'annual'.
        - `update_date` string, nullable — ONS updateDate for the observation (ISO 8601 UTC).
      - `rollups` object — Optional higher/lower frequency rollups keyed by 'annual', 'quarterly', or 'monthly'.
    - `cpi_annual_rate` OnsSeries, required — One curated ONS CDID series, unified shape regardless of parent dataset.
      - `cdid` string, required — ONS time series identifier (stable 4-char code, e.g. 'L55O', 'MGSX').
      - `title` string, nullable — Series title as published by ONS.
      - `unit` string, nullable — Unit of measure (e.g. '%', 'index 2015=100', 'GBP m', 'persons').
      - `frequency` string, required — Canonical frequency returned in `observations` ('monthly', 'quarterly', 'annual').
      - `observations` OnsObservation[], required — Observations at the canonical frequency, ordered oldest to newest.
        - `period` string, required — ISO 8601 start-of-period (YYYY-MM-DD). Months = first day of month, quarters = first day of quarter, years = January 1.
        - `period_label` string, required — Original ONS label, e.g. '2026 FEB', '2025 Q4', '2024', or rolling LFS label '2025 NOV-JAN'.
        - `value` number, nullable — Numeric observation value. Null if upstream reported an empty cell.
        - `frequency` string, required — Frequency of this row: 'monthly', 'quarterly', or 'annual'.
        - `update_date` string, nullable — ONS updateDate for the observation (ISO 8601 UTC).
      - `rollups` object — Optional higher/lower frequency rollups keyed by 'annual', 'quarterly', or 'monthly'.
    - `rpi_index` OnsSeries, required — One curated ONS CDID series, unified shape regardless of parent dataset.
      - `cdid` string, required — ONS time series identifier (stable 4-char code, e.g. 'L55O', 'MGSX').
      - `title` string, nullable — Series title as published by ONS.
      - `unit` string, nullable — Unit of measure (e.g. '%', 'index 2015=100', 'GBP m', 'persons').
      - `frequency` string, required — Canonical frequency returned in `observations` ('monthly', 'quarterly', 'annual').
      - `observations` OnsObservation[], required — Observations at the canonical frequency, ordered oldest to newest.
        - `period` string, required — ISO 8601 start-of-period (YYYY-MM-DD). Months = first day of month, quarters = first day of quarter, years = January 1.
        - `period_label` string, required — Original ONS label, e.g. '2026 FEB', '2025 Q4', '2024', or rolling LFS label '2025 NOV-JAN'.
        - `value` number, nullable — Numeric observation value. Null if upstream reported an empty cell.
        - `frequency` string, required — Frequency of this row: 'monthly', 'quarterly', or 'annual'.
        - `update_date` string, nullable — ONS updateDate for the observation (ISO 8601 UTC).
      - `rollups` object — Optional higher/lower frequency rollups keyed by 'annual', 'quarterly', or 'monthly'.
  - `meta` SugraMeta, required — Metadata attached to every /api/v1/* response envelope.
    - `endpoint` string, required — Requested endpoint path.
    - `data_time` string, required — ISO 8601 UTC timestamp of the source data, not of the request.
    - `response_time` string, required — ISO 8601 UTC timestamp when this response was produced.
    - `provider` string, required — API name and version.
    - `source` string, nullable — Identifier of the primary upstream source used for this response.
    - `attribution` string, nullable — Human-readable attribution mandated by an upstream source (e.g. a securities regulator or self-regulatory organization). Present only on responses whose source requires the owner and source to be clearly identified. Do not remove or alter it when using the response.
    - `fallback_used` boolean, nullable — True when the primary source failed and a fallback produced the data.
    - `fallback_chain` string[], nullable — Ordered list of sources attempted, in the order they were tried.
    - `cached` boolean, nullable — True when this response was served from the internal cache.
    - `stale` boolean, nullable — True when the cached response was returned after the upstream rate-limited or errored. Clients can use this to detect degraded data.

## Other responses

- `401` — Missing or invalid `x-api-key` header. JSON body with a stable `code` distinguishing `missing_api_key` (no header sent) from `invalid_api_key` (header sent, key not accepted); any other 401 source carries the generic `unauthorized` with its detail as `reason`. Plus `hint`. `plan` is always null on 401 - an unauthenticated request has no plan; quota exhaustion is 429, not 401.
- `422` — Validation Error
- `429` — Daily rate limit exceeded. Check `X-RateLimit-Reset` for the next window.
- `503` — Upstream source is temporarily unavailable. Retry after a short delay.

---

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