The Company Tax Return has three blocks of boxes for capital allowances: allowances and balancing charges that are part of the trading profit (688 to 730), the same analysis for allowances outside the trade (733 to 755), and the expenditure the claims are based on (760 to 775). None of them is typed in. Tax Optimiser fills them from the Assets section of the computation, and this page shows which entry feeds which box.
For how to use the Assets section step by step, read Capital allowances in the Corporation Tax series first. Depreciation, which capital allowances replace, is covered in Depreciation in your trial balance.
Which pool feeds which box
Every asset on the Fixed Asset Additions tab is given a pool, and the pool decides the allowance and the box.
| Pool in Tax Optimiser | Allowance | Allowance box | Expenditure box |
|---|---|---|---|
| Plant and Machinery | AIA if allocated, then 18% a year (14% from 1 April 2026) | 705, with AIA also in 690 | 775 |
| Special Rate | AIA if allocated, then 6% a year | 695, with AIA also in 690 | 770 |
| Full Expensing (100%) | 100% in the year of purchase | 688 | 760 |
| Special Rate 50% FYA | 50% in the year of purchase | 693 | 760 and 773 |
| Main Rate 40% FYA | 40% in the year of purchase | 696 | 760 |
| Structures and Buildings | 3% a year, straight line | 711 | 771 |
| Electric Vehicle Charge-Point (100% FYA) | 100% in the year of purchase | 713 | 760 |
| Zero-Emission Goods Vehicle (100% FYA) | 100% in the year of purchase | 723 | 760 |
| Energy Efficient Cars | 100% in the year of purchase | 726 | 760 |
The pool headings on the General tab carry the same box numbers, so you can check as you go.
A worked example
Example Plant Ltd makes a profit of £150,000 before capital allowances in the year to 31 March 2026. It brings forward a main pool of £20,000 and a special rate pool of £10,000, and buys two things in the year.
The machine goes into the main pool and is covered by the Annual Investment Allowance on the AIA Allocation tab. The racking is claimed under full expensing, which needs no allocation.
| Allowance | £ | Box | |
|---|---|---|---|
| Milling machine, £30,000 | AIA at 100% | 30,000 | 690 and 705 |
| Main pool brought forward, £20,000 | Writing-down allowance at 18% | 3,600 | 705 |
| Special rate pool brought forward, £10,000 | Writing-down allowance at 6% | 600 | 695 |
| Racking, £12,000 | Full expensing at 100% | 12,000 | 688 |
| Total allowances | 46,200 |
Taxable profit is £150,000 − £46,200 = £103,800, and the Corporation Tax is £23,757.00 after marginal relief.
At the foot of the General tab, Tax pools and allowances claimed shows the same movement pool by pool, and the written-down values to carry into next year: £16,400 and £9,400.
Why the boxes add up to more than the claim
On the return, box 690 shows £30,000 and box 705 shows £33,600. Add every box and you get £76,200, not £46,200. That is how HMRC designed the form, not a double claim:
- Box 705 (and 695 for the special rate pool) is the total allowance for the pool, including any AIA.
- Box 690 repeats the AIA by itself, as a memorandum.
The amount actually deducted from profits is the total in the computation, £46,200. Full expensing (688) and the other first-year allowances are never included in the pool boxes.
Boxes 688 to 730: allowances in the trading profit
Choose CT600 Boxes in Corp Tax Calculations and scroll to the capital allowances section to see these. Each line has an allowance box on the left and, where one applies, a balancing charge or disposal value box on the right.
Boxes 688 and 689: Full expensing
The 100% first-year allowance for new main-rate plant and machinery bought by a company on or after 1 April 2023. Cars, second-hand assets and assets bought to lease out do not qualify. Box 689 is the balancing charge when a fully expensed asset is sold: the proceeds are taxed straight away, because the asset never went into a pool.
Box 690: Annual investment allowance
The AIA claimed, from the AIA Allocation tab. AIA gives 100% on up to £1,000,000 of plant and machinery a year, new or second-hand, but not cars. The limit is reduced for a short period and shared across a group.
Boxes 691 and 692: Super-deduction
The 130% allowance for expenditure between 1 April 2021 and 31 March 2023. No new claims can arise, but box 692 still reports a balancing charge when a super-deduction asset is sold.
Boxes 693 and 694: Special rate allowance
The 50% first-year allowance for new special rate assets, such as integral features of a building. The other half of the cost goes into the special rate pool. Balancing charges in boxes 689, 692 and 694 come from the Fixed Asset Disposals tab.
Boxes 695 and 700: Special rate pool
Box 695 is the total allowance on the special rate pool: writing-down allowance at 6%, plus any AIA allocated to special rate expenditure. Box 700 is a balancing charge on the pool.
Box 696: 40% first-year allowance
The allowance for new main-rate plant bought on or after 1 January 2026, including assets for leasing, which full expensing does not cover. The remaining 60% joins the main pool in the following period.
Boxes 705 and 710: Main pool
Box 705 is the total allowance on the main pool: writing-down allowance at 18% (14% from 1 April 2026, with a blended rate for a period that spans the change), plus any AIA allocated to main pool expenditure. A pool with £1,000 or less left can be written off in full. Box 710 is a balancing charge, which arises when disposal proceeds are more than the pool.
Box 711: Structures and buildings
The structures and buildings allowance: 3% a year of the construction cost of a non-residential building, from the day it is brought into use. Switch on Structures and Buildings on the General tab to enter each building.
Boxes 713 and 714: Electric vehicle charge-points
The 100% first-year allowance for charge-point equipment, and the disposal value when it is sold. Tax Optimiser does not fill the disposal value boxes 714, 724 and 727; disposal proceeds are entered against the pool on the General tab.
Boxes 715 to 722: Business premises renovation and enterprise zones
Legacy and specialist allowances. Tax Optimiser has no pool for these.
Boxes 723 and 724: Zero-emission goods vehicles
The 100% allowance for new electric vans and lorries bought before 1 April 2025. See Electric vans and zero-emission goods vehicles.
Boxes 725 and 730: Other allowances and charges
Anything not covered above.
Boxes 726 and 727: Zero-emission cars
The 100% first-year allowance for a new electric car. Cars with emissions go into the main pool or the special rate pool according to their CO2 figure and never qualify for AIA or full expensing.
Boxes 733 to 755: allowances outside the trade
The same list again for a company whose assets are used in a UK property business or to manage its investments. Capital allowances claimed by at the top of the Assets section moves the whole analysis here: full expensing 733, AIA 735, structures and buildings 736, charge-points 737, the 40% allowance 739, zero-emission goods vehicles 748, zero-emission cars 751, and main and special rate pool allowances in 750. See UK property income and losses and Management expenses.
Boxes 760 to 775: qualifying expenditure
These report what was spent in the period, not what was claimed.
Box 760: Machinery and plant on which first-year allowance is claimed
Expenditure claimed under full expensing or any other first-year allowance. The racking in the example, £12,000.
Box 765: Designated environmentally friendly machinery and plant
Withdrawn for expenditure after 31 March 2020.
Box 770: Long-life assets and integral features
Special rate expenditure, including any covered by AIA, other than special rate cars.
Box 771: Structures and buildings
Qualifying construction expenditure, in the first period the allowance is claimed for the building.
Boxes 772 and 773: Super-deduction and special rate allowance expenditure
Expenditure claimed under those two allowances. It is also part of box 760.
Box 775: Other machinery and plant
Main pool expenditure, including any covered by AIA. The milling machine in the example, £30,000.
Things that go wrong
- An addition with no AIA. Putting an asset on Plant and Machinery does not claim AIA. Until you allocate it on the AIA Allocation tab, it only gets the 18% writing-down allowance.
- Pools not brought forward. Written-down values do not roll into the next period by themselves. Enter them in Write down allowance B/F, or click Use as written down allowance B/F when Tax Optimiser offers the previous period’s figures.
- Depreciation left in. Capital allowances replace depreciation; they do not sit on top of it. Depreciation in the accounts must be added back.
- Full expensing on something that does not qualify. Second-hand equipment and cars must go to a pool instead.
HMRC’s guidance: Claim capital allowances, Annual Investment Allowance and full expensing. Related: every CT600 box explained.
Common questions
Is AIA counted twice in boxes 690 and 705?
It appears in both, by HMRC’s design. Box 705 is the total main pool allowance including AIA, and box 690 shows the AIA separately. The deduction from profits is only made once.
Should I claim AIA or full expensing?
Both give 100% in the year of purchase. Full expensing has no limit but only covers new main-rate plant bought by a company. AIA is capped at £1,000,000 but also covers second-hand and special rate assets. When a fully expensed asset is sold the proceeds are taxed immediately, whereas proceeds of an AIA asset reduce the pool.
Which box does a company car go in?
A new electric car gets 100% in box 726. Any other car goes into the main pool (box 705) or, with higher emissions, the special rate pool (box 695).
Do I have to claim capital allowances?
No. A company can claim less than the maximum, or nothing, and keep the value in the pool for later years. That can be worthwhile when profits are already covered by losses.
What is a balancing charge?
Tax relief given back. It arises when an asset is sold for more than the value left in its pool, or when a fully expensed asset is sold at all, and it is added to the taxable profit.
Where do capital allowances for a rental property go?
In boxes 733 to 755. Set Capital allowances claimed by to UK property business at the top of the Assets section.
What happens to the pools when the trade stops?
No AIA, first-year or writing-down allowances are due in the final period. Whatever is left in each pool after disposal proceeds becomes a balancing allowance, or a balancing charge if it is negative. Tick Trade ceased in this period on the Assets section.