CT600F is the tonnage tax supplementary page of the Company Tax Return. A shipping company that has elected into tonnage tax is taxed on a notional profit worked out from the size of each ship, instead of on the profit its shipping trade actually made. This guide explains when the page is needed, how the profit is worked out, how to complete the page in Tax Optimiser, and what each box from F1 to F70 means.
When a company needs a CT600F
File a CT600F, and tick box 120 on the CT600, if the company operates or manages qualifying ships and is party to a tonnage tax election. The election is made separately with HMRC and normally lasts ten years; the CT600F is how each year’s tonnage tax profits are reported.
A company that is not within a tonnage tax election does not file the page.
How tonnage tax profits are worked out
Each qualifying ship has a daily profit based on its net tonnage, rounded down to a multiple of 100 tons. The rate for each 100 tons depends on the band:
| Net tonnage | Ship operated | Ship managed only |
|---|---|---|
| Up to 1,000 tons | £0.60 | £0.12 |
| From 1,000 to 10,000 tons | £0.45 | £0.09 |
| From 10,000 to 25,000 tons | £0.30 | £0.06 |
| Above 25,000 tons | £0.15 | £0.03 |
The daily profit is multiplied by the number of days in the period that the company operated or managed the ship. For example, a ship of 12,345 net tons counts as 12,300 tons: 10 × £0.60 + 90 × £0.45 + 23 × £0.30 = £53.40 a day, or £16,020 for 300 days.
The profits of all the ships are added up, rounded down to the pound, and charged to Corporation Tax in box 200 of the CT600. No loss, relief or other deduction can be set against them.
Completing the CT600F in Tax Optimiser
Open the period’s Corp Tax Calculations workspace and choose Tonnage Tax in the Sections menu. If the period of account is longer than 12 months it is filed as two returns, each with its own CT600F; use the Return 1 and Return 2 buttons to switch between them and enter the ships, days and figures for each return.
Step 1 — Say that the page applies
Tick The company is within a tonnage tax election for this period. This is what attaches the CT600F to the return.
Step 2 — Answer the Part 1 questions
Say whether the company is party to a group election (and name the group), whether it was covered by a training certificate, whether the limit on chartered-in tonnage was met, and whether the special rules for offshore activities apply. Tax Optimiser only shows the questions that apply: with a group election the company’s own chartering limit is filed as Not applicable, and for periods starting on or after 1 April 2022 the flagging questions are filed as Not applicable.
Step 3 — Enter the accounts figures in Part 3
Enter the profit or loss in the accounts from the tonnage tax activities. Enter a loss as a negative figure. Tax Optimiser takes this figure out of the trading profit in the computation, because the tonnage tax profits are charged in its place. If the company has other trades or income, leave those in the usual sections.
Also enter any profit or loss on the disposal of tonnage tax assets and any dividends that qualify as relevant shipping income. These two are reported to HMRC for information and do not change the calculation.
Step 4 — Add the ships in Part 4
Click Add ship for each qualifying ship and enter its name, IMO number, the company’s interest in it, its gross and net tonnage and the days operated or managed. The profit for the ship is worked out for you. If the company holds a joint interest in a ship with another operator, enter its share as a percentage; otherwise leave the share at 100.
Step 5 — Save and check the return
Click Save. Once the page applies, Tax Optimiser:
- ticks box 120 on the CT600;
- carries the total in F70 to box 200, and from there into the profits chargeable and the tax;
- takes the accounts profit in F55 out of the trading profit (or adds a loss back);
- adds any offshore training allowance in F45 to box 450;
- files the CT600F with the return and adds a Tonnage tax 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, clear the first tick and save.
CT600F box by box
Boxes F1 to F4 — 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.
Boxes F5A and F5B — Tonnage tax group election
Yes if the company was a party to a tonnage tax group election, No if it elected on its own.
Box F10 — Name of the tonnage tax group
The name of the group the company was a member of at the end of the period. Only completed when F5A is Yes.
Boxes F15A to F15C — Training certificate
Whether the company or group was covered by a Department for Transport certificate approving its training commitment. Choose Not applicable if the company or group manages qualifying ships but does not operate any.
Boxes F20A to F20C — Company limit on chartered-in tonnage
Whether the company kept within the limit: no more than 75% of the net tonnage of the ships it operates may be chartered in, other than on bareboat charter. Filed as Not applicable when the company is in a group election.
Boxes F25A to F25C — Group limit on chartered-in tonnage
The same test for the group’s tonnage as a whole. Only completed with a group election. Choose Not applicable if the company is not the group’s representative company.
Boxes F30A to F30C — Ships not registered in the UK for the first time
Part of the old flagging rules, which were repealed for periods starting on or after 1 April 2022. For those periods the answer is always Not applicable (F30C).
Boxes F35A and F35B — Flagging conditions
Only completed when F30A is Yes, so it is left blank for periods starting on or after 1 April 2022.
Boxes F40A and F40B — Offshore activities
Yes if the company is subject to the special rules for ships engaged in offshore activities on the UK continental shelf.
Box F45 — Training allowance to offset
The offshore training allowance set against the Corporation Tax liability. It is included in box 450 of the CT600 and cannot be more than the tax left to set it against. Only completed when F40A is Yes.
Box F50 — Training allowance carried forward
The offshore training allowance that could not be used in this period.
Boxes F55A and F55B — Profit or loss in the accounts
The accounts profit (F55A) or loss (F55B) from the tonnage tax activities, leaving out anything entered in F60 or F65.
Boxes F60A and F60B — Disposal of tonnage tax assets
The accounts profit or loss on disposing of tonnage tax assets, which would otherwise be dealt with under the chargeable gains rules.
Box F65 — Dividends and other distributions
Distributions from overseas shipping companies that qualify as relevant shipping income.
Box F70 — Tonnage tax profits
The table lists each ship: name (A), IMO number (B), interest (C), gross tonnage (D), net tonnage (E), days operated or managed (F), tonnage tax profits (G), whether it was on the UK register (H) and whether it was operated or managed for the first time in the period (I). The interest is O for owned or bareboat chartered in, F for finance leased, T for time or voyage chartered in, G for chartered from another member of the group, and M for managed only. F70 is the total of column G, rounded down to the pound, and is copied to box 200.
The printed form holds ten ships. If the company has more, Tax Optimiser adds continuation sheets and shows F70 on the last one.
What Tax Optimiser does not do
Tax Optimiser does not make or renew the tonnage tax election, decide which ships or activities qualify, or test the training and chartering conditions for you. It does not ring-fence capital allowances automatically: assets used for the tonnage tax trade do not qualify for capital allowances, so leave them out of the Capital Allowances section. Gains on tonnage tax assets and the exit charges on leaving the regime are not calculated. These are judgements for the company and its advisers.
Common questions
What is the CT600F?
The CT600F is the supplementary page of the Company Tax Return for companies within tonnage tax. It lists the qualifying ships and works out the tonnage tax profits. Box 120 on the CT600 is ticked to show it is attached.
Who has to complete a CT600F?
A company that operates or manages qualifying ships and is party to a tonnage tax election, for each accounting period the election is in force.
How is the tonnage tax profit of a ship calculated?
The net tonnage is rounded down to a multiple of 100 tons and charged at a daily rate for each 100 tons, from £0.60 for the first 1,000 tons down to £0.15 above 25,000 tons. The daily profit is multiplied by the days the ship was operated in the period. Ships that are only managed use rates one fifth of those.
Where do tonnage tax profits go on the CT600?
Box F70 on the CT600F is copied to box 200 on the CT600, where it forms part of the profits chargeable to Corporation Tax.
Can losses be set against tonnage tax profits?
No. No loss, relief or other deduction can reduce tonnage tax profits, and a loss on the tonnage tax trade itself is not available for relief.
What happens to the shipping profit in the accounts?
It is left out of the taxable trading profit, because the tonnage tax profits are charged instead. Enter it in box F55 and Tax Optimiser makes the adjustment in the computation.
Do I still complete boxes F30 and F35?
For periods starting on or after 1 April 2022 the flagging rules no longer apply, so F30 is filed as Not applicable and F35 is left blank.
Where to go next
- Corporation Tax in Tax Optimiser — the full journey from trial balance to filed return.
- CT600 box-by-box guide — box 200 and the supplementary page boxes on the main return.
- HMRC’s CT600F guidance — the official notes for the page.