Guide Unilateral undertakings, section 106 agreements, habitat mitigation and affordable housing contributions

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4. Commuted sum calculator stage 1a

Commuted Sum Calculator part 1a

To calculate your affordable housing contribution you need to follow the 3 stage process. 

Affordable housing thresholds

The thresholds (number of homes on a scheme) where affordable housing can be required are established in a combination of National and Local Planning Policy  and vary by location. 

Our adopted Local Plan policy on affordable housing requires contributions to be sought from all sites for between 6-9 dwellings in the designated rural areas and from development of major residential dwellings or more (10 dwellings or more or sites in excess of 0.5ha) in the parishes of Exmouth, Sidmouth, Honiton and Seaton. See the Adopted Affordable Housing SPD for more information.

For major residential development within Exmouth, Sidmouth, Honiton and Seaton, the affordable housing should be provided on site.

In the designated rural areas where between 6-9 dwelling are proposed, a financial contribution will be payable.

Stage 1a - Establish if your scheme is required to make a contribution to affordable housing:


Major residential Development

(10 dwellings or more or 0.5ha in size)

1 - 5 dwellings

6-9 dwellings

Urban Areas:

Exmouth Wards: Exmouth Town, Littleham, Brixington,Halsdon, Withycombe Raleigh

Honiton Wards: St Michaels and St Paul’s.

Seaton and Sidmouth Urban Parishes.

Yes – on-site affordable housing required






All other wards in East Devon are classed as Rural Areas under the Housing Act for this purpose (including Sidbury Parish)

Yes – on-site affordable housing required


Yes – Financial Contribution required

The council may accept off-site cash contributions on larger sites, in lieu of onsite provision, where this is clearly justified by planning or other reasons.  On larger sites these will only be accepted by the council in exceptional circumstances and after all options for on-site delivery have been fully explored and discounted. There may also be some circumstances where the need in an area is such that on-site provision is required rather than a financial contribution for developments of less than 10 dwellings in the designated rural areas.

On some sites, it may simply not be possible to meet full the requirement for affordable housing through on-site provision e.g. 25% affordable housing of 14 dwellings is 3.5 dwellings.   In this example three  affordable dwellings could be provided on site and the requirement for the remaining 0.5 unit be met by a commuted payment.

Having decided that the council needs to collect a commuted sum, it is important that there is a consistent and transparent mechanism for calculating the commuted sum to be collected. The Council uses a Commuted Sum Calculator (CSC) for this purpose.  More information about the calculator.