CT600M is the supplementary page of the Company Tax Return for companies claiming the enhanced capital allowances available in the special tax sites of Freeports and Investment Zones. This guide explains when the page is needed, what the two allowances are, how to complete the page in Tax Optimiser, and what each box from M1 to M30 means.
When a company needs a CT600M
File a CT600M, and tick box 143 on the CT600, if the company claims either of these for a Freeport or Investment Zone tax site:
- the enhanced structures and buildings allowance — 10% a year on the cost of a qualifying building or structure, instead of the usual 3%;
- the enhanced capital allowance — a 100% first-year allowance on new plant and machinery bought mainly for use in the tax site.
A company with no claims for a special tax site does not file the page.
Completing the CT600M in Tax Optimiser
Open the period’s Corp Tax Calculations workspace and choose Freeports in the Sections menu. If the period of account is longer than 12 months it is filed as two returns, each with its own CT600M; use the Return 1 and Return 2 buttons to switch between them and enter each claim in the return it belongs to.
Step 1 — Add each structure or building
Click Add structure or building for each building the company claims the enhanced allowance on. Choose the Freeport or Investment Zone, enter the address, the two dates, the qualifying expenditure and the allowance claimed for the period.
Only enter the qualifying expenditure in the year the allowance is first claimed. In later years leave it at nil and enter just the allowance.
Step 2 — Add each plant and machinery claim
Click Add plant and machinery claim for each Freeport or Investment Zone where the company bought qualifying plant or machinery. Enter the allowance claimed, any disposal value, and tick the box if an Enterprise Zone claim was also made.
Step 3 — Keep these assets out of the Capital Allowances section
The allowances entered on this page are deducted in the computation. Do not also enter the same buildings or plant in the Capital Allowances section, or the allowance will be given twice.
Step 4 — Save and check the return
Click Save. Once a claim is entered, Tax Optimiser:
- ticks box 143 on the CT600;
- deducts the allowances claimed (M15 and M25) from the trading profit, or from the property or investment business if that is where the company’s capital allowances belong;
- includes the structures and buildings allowance in box 711 (or box 736 outside a trade) and its qualifying expenditure in box 771;
- includes the plant and machinery claim in box 760;
- files the CT600M with the return and adds a Freeports and Investment Zones page to the computation;
- lists the completed form under Supplementary pages on the CT600 Document card, where you can view or download it.
To remove the page, delete the rows and save.
CT600M box by box
Boxes M1 to M4 — Company information
The company name, tax reference and the period covered by the page. Tax Optimiser copies them from the return; the period cannot exceed 12 months.
Box M5 — Enhanced structures and buildings allowances
One row for each structure or building.
- A — Location. HMRC’s code for the Freeport or Investment Zone. Tax Optimiser files the code for the location you choose.
- B — Address of business operation. At least two lines.
- C — Date brought into qualifying use. The later of the date the structure or building was brought into qualifying use and the date the qualifying expenditure was incurred.
- D — Date of first contract for construction. If there was no contract, or construction began before one was made, the date construction began.
- E — Total amount of qualifying expenditure. Only when the company is the first to claim and is claiming for the first time. Enter nil if the allowance was claimed before, by the company or an earlier owner.
- F — Total structures and buildings allowance claim amount. The enhanced allowance claimed for the period. If a building straddles the boundary of a tax site, leave out the part that only qualifies for the ordinary allowance and enter that in the Capital Allowances section instead.
Box M10 — Total qualifying expenditure
The total of column E. Calculated automatically and included in box 771 of the CT600.
Box M15 — Total SBA claim amount
The total of column F. Calculated automatically and included in box 711 of the CT600, or box 736 where the allowances are not claimed in a trade.
Box M20 — Enhanced capital allowance for plant and machinery
One row for each Freeport or Investment Zone.
- A — Location and B — Address of business operation, as for M5.
- C — Enterprise Zone claim. An ‘X’ if the site is also in an Enterprise Zone and a claim was made for the plant or machinery under those rules.
- D — Total amount of ECA claimed. The allowances claimed on plant or machinery bought mainly for use in a tax site. If the full allowance is claimed, this is the expenditure incurred.
- E — Disposal value. Any amount brought into account on a disposal of the plant or machinery, even if no balancing charge arose.
Each row needs at least one of C, D and E.
Box M25 — Total ECA claimed
The total of column D. Calculated automatically and included in box 760 of the CT600 with any other first-year allowance expenditure.
Box M30 — Total disposal value
The total of column E. Calculated automatically.
The printed form holds twelve rows in each table. If the company has more, Tax Optimiser adds continuation sheets and shows the totals on the last one.
Location codes
| Code | Freeport | Code | Investment Zone |
|---|---|---|---|
| 1 | East Midlands Airport | 13 | Liverpool City Region |
| 2 | Felixstowe and Harwich | 14 | North East |
| 3 | Humber | 15 | West Midlands |
| 4 | Liverpool City Region | 16 | East Midlands |
| 5 | Plymouth and South Devon | 17 | Flintshire and Wrexham |
| 6 | Solent | 18 | North East of Scotland |
| 7 | Thames | 19 | Glasgow City Region |
| 8 | Teesside | ||
| 9 | Inverness and Cromarty Firth | ||
| 10 | Forth | ||
| 11 | Anglesey | ||
| 12 | Celtic (Port Talbot and Milford Haven) |
What Tax Optimiser does not do
Tax Optimiser does not work out the enhanced allowances from an asset register, check that a building or item of plant is inside a designated tax site, or test the other conditions for the reliefs; you enter the amounts claimed. A disposal value in M20 is reported only: if it gives rise to a balancing charge through a pool, enter that in the Capital Allowances section. The other Freeport reliefs, for employer National Insurance, Stamp Duty Land Tax and business rates, are not part of the Company Tax Return.
Common questions
What is the CT600M?
The CT600M is the supplementary page of the Company Tax Return for the enhanced capital allowances in Freeport and Investment Zone tax sites. Box 143 on the CT600 is ticked to show it is attached.
Who has to complete a CT600M?
A company claiming the enhanced structures and buildings allowance, or the enhanced capital allowance for plant and machinery, for a special tax site in a Freeport or Investment Zone.
What is the enhanced structures and buildings allowance?
A structures and buildings allowance of 10% a year, rather than 3%, on the cost of a qualifying building or structure in a special tax site, so the cost is relieved over ten years.
What is the enhanced capital allowance?
A 100% first-year allowance on new and unused plant and machinery bought mainly for use in a special tax site.
Where do the CT600M figures go on the CT600?
Box M10 is included in box 771, box M15 in box 711 or 736, and box M25 in box 760. Tax Optimiser does this for you.
Do I enter the qualifying expenditure every year?
No. Enter it in column E only in the year the allowance is first claimed. In later years enter nil in column E and the allowance for the year in column F.
Should I also enter the asset in the Capital Allowances section?
No. The claim on the CT600M is deducted in the computation, so entering the same asset in the Capital Allowances section would give the allowance twice.
Where to go next
- Corporation Tax in Tax Optimiser — the full journey from trial balance to filed return.
- CT600 box-by-box guide — boxes 711, 736, 760 and 771 and the supplementary page boxes on the main return.
- HMRC’s CT600M guidance — the official notes for the page.