The Income Deprivation Affecting Children Index (IDACI) is a specific sub-domain of the Index of Multiple Deprivation (IMD), which is the official measure of relative deprivation for small areas in England. It focuses exclusively on children under the age of 16 who are living in families that are classified as income deprived. Income deprivation is defined here as households that are in receipt of certain means-tested benefits, such as Income Support, Jobseeker’s Allowance, or Universal Credit (where the household income is below a threshold), or that are in families with low income and in receipt of tax credits. In short, IDACI tells you what share of children in a given small area are growing up in low-income households.
How IDACI fits into the UK geography and postcode system
IDACI is calculated at the level of Lower-layer Super Output Areas (LSOAs) in England. LSOAs are small statistical geographies, each containing roughly 400 to 1,200 households and around 1,500 residents. They are designed to be stable over time and are the building blocks for many official statistics. Postcodes are not directly used as the unit for IDACI; instead, each postcode is assigned to an LSOA, and the IDACI score for that LSOA is then applied to every postcode within it. This means that if you look up a postcode, you can find the IDACI rank or decile for the LSOA that contains that postcode. The Office for National Statistics (ONS) provides lookup tables that link postcodes to LSOAs, so it is straightforward to map a postcode to its IDACI value.
How IDACI relates to postcodes specifically
When you search for a postcode on a website like Postcodes UK, the IDACI value you see is not a property of the postcode itself but of the LSOA that the postcode falls within. For example, a single postcode might cover a handful of addresses, but the IDACI score applies to the entire LSOA of perhaps 600 addresses. This is because the data used to calculate IDACI comes from administrative sources like benefit records, which are aggregated to LSOA level to protect individual privacy. So while IDACI is a useful indicator for a postcode, it is important to remember that it reflects the broader neighbourhood rather than the specific street or building. The most common way IDACI is presented is as a decile, where 1 is the most deprived 10 per cent of LSOAs nationally and 10 is the least deprived. A postcode in an LSOA with an IDACI decile of 1 means that area is among the most deprived in the country for child income deprivation.
Why IDACI matters for researching an area
For anyone researching a neighbourhood, IDACI provides a quick and reliable snapshot of child poverty. It is widely used by local authorities, schools, and charities to target resources such as free school meals eligibility, early years support, or community programmes. For homebuyers or renters, a high IDACI decile (that is, a low deprivation rank) might indicate an area with fewer children in poverty, which can sometimes correlate with better school outcomes or lower crime rates, though this is not always straightforward. Researchers use IDACI alongside other IMD domains, such as health deprivation or crime, to build a fuller picture. Because IDACI is updated roughly every two to four years with each new release of the IMD, it is a current and reliable measure. However, it only captures income deprivation, not other forms of disadvantage like lack of access to services or poor housing. So while IDACI is a powerful tool, it should be used as part of a wider assessment of an area, not as the sole indicator.