Community Infrastructure Levy (CIL) payable or not?

Ah I think the question here is will they consider the whole building a new development, which makes the 99m2 increase the red herring.

From .Gov >> https://www.gov.uk/guidance/community-infrastructure-levy

"What kind of development is liable for the levy?

The levy may be payable on development which creates net additional floor space, where the gross internal area of new build exceeds 100 square metres (the Rates section explains how this is calculated). That limit does not apply to new houses or flats, and a charge can be levied on a single house or flat of any size, unless it is built by a ‘self builder’ (see Self build exemption and regulation 54A and 54B).

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Revision date: 12 06 2014
What kind of development does not pay the levy?

The following do not pay the levy:

development of less than 100 square metres (see regulation 42 on minor development exemptions) – unless this is a whole house, in which case the levy is payable
houses, flats, residential annexes and residential extensions which are built by ‘self builders’ (see regulations 42A, 42B, 54A and 54B, inserted by the 2014 Regulations)
social housing that meets the relief criteria set out in regulation 49 or 49A (as amended by the 2014 Regulations)
charitable development that meets the relief criteria set out in regulations 43 to 48
buildings into which people do not normally go (see regulation 6(2))
buildings into which people go only intermittently for the purpose of inspecting or maintaining fixed plant or machinery (see regulation 6(2))
structures which are not buildings, such as pylons and wind turbines
specified types of development which local authorities have decided should be subject to a ‘zero’ rate and specified as such in their charging schedules
vacant buildings brought back into the same use (see regulation 40 as amended by the 2014 Regulations)

Where the levy liability is calculated to be less than £50, the chargeable amount is deemed to be zero so no levy is due.

Mezzanine floors, inserted into an existing building, are not liable for the levy unless they form part of a wider planning permission that seeks to provide other works as well."

"How does the levy relate to planning permission?

The levy is charged on new development. Normally, this requires planning permission from the local planning authority, the Planning Inspectorate, or the Secretary of State on appeal.

Planning permission can also be granted through local planning orders. Examples are simplified planning zones and local development orders (see related National Planning Policy Guidance on Local Development Orders). Development can also be granted consent by Neighbourhood Development Orders (see related guidance), including Community Right to Build Orders. Some Acts of Parliament, such as the Crossrail Act 2008, also grant planning permission for new buildings.

The levy applies to all these types of planning consent.

The levy may also be payable on permitted development (see related guidance on the General Permitted Development Order).

Development which is the subject of a Lawful Development Certificate may be liable for the levy, depending on the circumstances. A lawful development certificate (granted under section 191 or 192 of the Town and Country Planning Act 1990) is often sought to confirm permitted development rights. It does not by itself trigger a levy payment because it is not a planning permission as defined in regulation 5. It simply confirms that no further application for planning permission is needed for the development described in the certificate. So where a certificate is sought to confirm permitted development rights, the normal levy provisions in respect of permitted development rights apply, and the grant of such a certificate is not relevant to whether or not, or when, the levy may be payable.

Where a planning permission is phased, each phase of the development is treated as if it were a separate chargeable development for levy purposes (see regulation 8(3A) as amended by 2014 Regulations). This may apply to schemes which have full planning permission as well as to outline permissions. For further details, see ‘When does a charging schedule come into effect?’ and ‘Is there another way to allow phased payments’."

Reply to the comment left by Neil Patterson at 25/01/2018 - 11:49
a perfect example of legislation put together by a committee to serve the interests of lawyers?

Reply to the comment left by terry sullivan at 26/01/2018 - 10:32
Quite right.
Committte of the lawyers, by the lawyers, for the lawyers.
Same same our politicians. Do we need 650 of them to represent us ? Each n every one of them has to justify his/her existence. That’s why we r legislated to death.