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Background Notes and Methodology

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The analysis in this publication is based primarily on data-linking of pseudonymised data sources held by the Central Statistics Office. The main data source was the Residential Tenancy Board (RTB). This has information on registered rental tenancies, including details on properties, landlords and tenants.

The following data sources were also used and were either linked to, or compared with, the RTB data.

  • Building Energy Rating (BER) assessments data compiled by the Sustainable Energy Authority Ireland (SEAI)
  • Person Income Register (PIR)
  • PAYE Real Time Data
  • Central Record System (CRS)
  • Income Tax Form 11
  • Local Property Tax (LPT)
  • Housing Assistance Payment (HAP)
  • Directory of Irish Property Addresses (Geo Directory)
  • Central Business Register (CBR)
  • Student Universal Support Ireland (SUSI)

The linkage and analysis were undertaken by the CSO for statistical purposes in line with the Statistics Act, 1993 and the CSO Data Protocol.

Before using personal administrative data for statistical purposes, the CSO removes all identifying personal information, including the PPSN and Eircode. The Personal Public Service Number (PPSN) is a unique number that enables individuals to access social welfare benefits, personal taxation and other public services in Ireland. The CSO removes the PPSN and creates a pseudonymised Protected Identifier Key (PIK). The PIK is a unique and non-identifiable number which is internal to the CSO. A similar process is undertaken to create an Eircode PIK. Using the PIKs enables the CSO to link and analyse data for statistical purposes, while protecting the security and confidentiality of the individual data. All records in the matched datasets are pseudonymised and the results are in the form of statistical aggregates which do not identify any individuals.

Rounding on Graphs and Tables

In some instances, numbers in the graphs and PxStat tables which form proportional distributions have been tweaked to ensure that the sum of the figures when rounded to one decimal place still equal 100.

Data Sources

Residential Tenancies Board (RTB) Register

The Residential Tenancies Board (RTB) register contains information on all tenancies registered by landlords, both private and Approved Housing Bodies (AHB). This contains details of associated tenants, properties and landlords. The RTB data does not include all tenants, as landlords may not provide details of all tenants in a tenancy. We can also expect that there is an unknown number of rental tenancies not registered with the RTB.

Building Energy Rating (BER) Assessments Data Compiled by the Sustainable Energy Authority Ireland (SEAI)

This includes assessments done for the Building Energy Rating (BER). The rating covers annual energy use, (based on a standard pattern of occupancy), for space heating, water heating, ventilation and lighting. Buildings are rated from A to G where A-rated homes are the most energy efficient.

Person Income Register (PIR) 

The PIR is a pseudonymised income register held internally within the CSO. It contains information on income received by individuals relating to employment, self-employment and social transfers. It is derived from administrative holdings held by the Revenue Commissioners and Department of Employment Affairs and Social Protection. Therefore, the PIR provides a near complete picture on individual level income, for a calendar year.  All linkage is carried out by using a PIK assigned on each contributing data source. The PIK is then used to link the pseudonymised data sources together to create the PIR. The PIK protects a person’s identity but also enables linking across data sources and over time. The PIK enables high quality deterministic matching thus significantly reducing/eliminating linkage error.

PAYE Real-Time Data

This dataset from Revenue has information on payroll returns at employee level in real-time. It has been available since 2019.

Income Tax Form 11

The Income Tax Form 11 has the annual income tax returns of self-assessed taxpayers, who are either self-employed or have non-PAYE income, (such as rental income).

Housing Assistance Payment (HAP) data

This data has details of all tenancies, tenants, properties and landlords involved in the HAP scheme since it started in 2014. More information on HAP can be found at The CSO received a dataset which was a copy of the live tables on 4 June 2020, which had all relevant records from the start of the scheme until this date.

Central Records System (CRS)

The Central Records System (CRS) is located in the Department of Employment Affairs and Social Protection (DEASP). It holds data on their customers, including identifying data such as address, relationships, claims, PPS contributions, earnings, employments and employers. It is a central repository of all the personal data on individuals held on different systems in the DEASP.

Local Property Tax (LPT)

This dataset details local property tax (LPT) returns from all liable residential properties on an annual basis. The CSO has added an identifier to the dataset indicating properties which are owned by local authorities.

Central Business Register (CBR)

The CSO's Central Business Register (CBR) is a register of all economic enterprises in Ireland and serves as the backbone in the production of economic statistics in Ireland. The CBR integrates administrative data, survey data, and large enterprise profiling work, and provides a live link to satellite registers within the CSO. 

Income and Employment Definitions

Rental Income

Unless otherwise stated this is the annual net residential rental income as indicated on self-assessed tax returns (IT Form 11 - see above). This is net of allowable expenses but is before taxes are applied (it is essentially the residential rental income which is taxable). The relevant amount from the main filer and their spouse is included in the figures in this report. This is the same as the Residential Rental Income source as detailed below and in Figure 3.3 and 3.4 (therefore Commercial Rental Income is not included in the 'Rental Income' figures detailed elsewhere in the Landlords chapter).

For more details on the allowable expenses on rental income see the Revenue guidelines. Expenses can vary year on year and could be higher in particular years. It is therefore possible that the net residential income of self-assessed returns could be very low, or even negative, when this is applied in a given year. For this reason, there are a very small number of unusual situations where landlords with a large number of rental tenancies have unexpected income sources as their primary source of income because for the year examined - 2019 - high expenses have rendered their rental income to be minimal.  

Instances where a landlord has not been able to be linked to any rental income have been excluded from all analysis of rental income in the report.

Gross Total Income

The annual gross income before deductions, such as tax and social insurance. This includes the following sources of income:

  • Employee Income - Employee portion of PAYE gross pay
  • Self-employed income - adjusted net profit from self-assessed tax return
  • Director income - director portion of PAYE gross pay
  • State pensions - includes State Pension (contributory and non-contributory), Widow’s, Widower’s or Surviving Civil Partner’s Contributory Pension
  • Residential Rental income - Gross income from residential rent less allowable expenses from self-assessed tax return 
  • Commercial Rental income - Gross income from commercial rent less allowable expenses from self-assessed tax return
  • Social welfare income - Total annual payments from the Department of Employment Affairs and Social Protection (excluding state pensions)
  • Private & Occupational pensions - Pensioner portion of PAYE gross pay
  • Income from higher & further education grants

Excluded from the income measure are:

  • Investment income, including saving accounts, bonds, stocks and shares
  • Income from foreign rental property
  • Community Employment Programme income

Where stated, income from years other than 2019 is inflation adjusted based on changes in the CPI (2011 base) between the December CPI of the relevant year and the December CPI of 2019.

Instances where a landlord or tenant has not been able to be linked to any income have been excluded from all relevant analysis within the report.

Disposable Income

The disposable income is the total gross income minus:

  • Tax, employee PRSI and USC deducted from PAYE gross pay (including from employee, director and pensioner portions)
  • Estimated tax, PRSI and USC from self-employed income (including adjusted net profit from self-assessed tax return and net residential and commercial rental income) 
  • LPT deducted through PAYE

Instances where a tenant has not been able to be linked to any income or where their calculated disposable income is less than their calculated rent have been excluded from all relevant analysis within the report.

PAYE Employment & Self Employed

Persons with less than €500 annual gross pay from PAYE employee income are not considered to be in PAYE employment (as detailed in Figure 3.5), nor are those with less than two weeks of PAYE employment

Persons with less than €500  self-employed trading income are not considered to be self-employed (as detailed in Figure 3.5), nor are those with less than two weeks of self-employed trading

NACE Classification

For the NACE sector categorisation of landlords, (as detailed in Figure 3.10 and 3.11), each person is attributed to the NACE sector of the PAYE employment for which they have the highest gross pay in the year; or if total self-employed profit is greater than PAYE income then this is the NACE sector of their primary trade. Only those with €500 or more of PAYE gross pay and two or more weeks of employment are included.

Other Definitions

Tenant Rent

The rent for the tenant used in the calculation of rent as percentage of disposable income (Map 4.1-Map 4.4) is calculated from the tenancy rent provided within the RTB datasets. This is self-reported by the landlord. Individual tenant rent is estimated by calculating the annual rent from what is provided for the tenancy and dividing this by the self-reported number of occupants associated with the rental property.

Tenants are excluded from the analysis in the following circumstances:

  • Where the number of occupants is not provided for the property or this is more than four (to avoid more likely scenarios associated with a larger amount of reported occupants where this doesn't match the actual number of occupants)
  • Where the tenant cannot be linked to any income or their total income is less than their calculated individual annual rent 
  • Where a rent amount is not provided
  • Where the tenancy started prior to 2018 (as the rent amount given for older tenancies may not be updated since the tenancy started and so is more likely to be out of date)
  • Where the property is owned by an Approved Housing Body or the tenant is in receipt of Housing Assistance Payment in 2019 (as the rent amount provided may include subsidies and therefore not relate to what the tenant is actually paying)
  • Where the calculated individual annual rent amount is less than €100 or greater than €50,000 (to exclude unlikely and nominal amounts)
  • Where the property of the tenant cannot be assigned to a local authority/local electoral area


All geographical analysis is based on latest available boundaries. This includes analysis related to time periods prior to boundary changes. For example, all local authority level analysis in Cork is based on property location in relation to the new boundaries after changes in May 2019. All geographical distribution within the report is based on the address of rental properties within the RTB dataset. Local authorities and Local Electoral Areas (LEAs) are assigned through geocoding of addresses undertaken within the CSO (including using provided Eircodes). It was not possible to assign these geographies to all address with sufficient accuracy. These addresses are not included within the relevant analysis. This is also the case for the geocoding of Eircodes within the BER and LPT datasets. This explains some of the unmatched properties between RTB and these datasets (see Table 2.1).

Non-Household Landlords and Owners

The numbers of non-household owners (and their properties) used in the Landlords chapter from Figure 3.12 was taken from the LPT. These are the owners of residential property which have a tax registration number provided, (i.e. they are a company rather than an individual). The properties are not necessarily all rented out as some could be vacant at any point in time. The detailed NACE classification attributed towards an institution was obtained from the CBR by linking on the tax registration number provided within the LPT data.

The company reference numbers provided within the RTB data for non-household landlords are not always of sufficient quality to accurately assess individual companies and obtain business classifications. This is why the analysis on non-household owners of properties is based on data from the LPT where the reference numbers are of better quality.

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