Mastering the UK Company Tax Return: An In-Depth Guide

Mastering the UK Company Tax Return: An In-Depth Guide


Filing a corporation tax return in the UK is critical for businesses to maintain compliance with legal obligations and avoid penalties. A company tax return (including form CT600 and other supporting documents) is a report that companies must submit to HMRC to declare their income, expenses, and taxes.

The following blog offers a detailed guide on how to complete a CT600 company tax return form for corporation tax. Keep reading to find out.


Company Information

Before completing the CT600 return form, it is important to fill out some basic company information, which includes the following:

  • Registered name of the company
  • Company registration number at Companies House
  • Unique taxpayer reference
  • Type of company: Enter the number that corresponds to your company (enter 0 if none of these types apply):
  1. Unit trust or open-ended investment company
  2. Close-investment holding company
  3. Company in the second or later year of liquidation
  4. Qualifying asset holding company
  5. Insurance
  6. Members’ club or voluntary association
  7. Property management company
  8. Charity or owned by a charity
  9. Real estate investment trust C: residual company
  10. Real estate investment trust C: tax-exempt company


About the CT600 Return Form

The CT600 form includes sections for income, expenses, and tax calculations. Individuals should ensure that all parts of this form are filled out. Enter the following information in these parts as follows:

  1. The beginning date of the period return (box 30) and end date (box 35). This period cannot begin before 1st April 2015.
  2. X if a repayment is due for this period (40). Entering bank or building society details in boxes 920 to 940 can speed up this process.
  3. X if a claim is made to reduce corporation tax liability for an earlier period (45).
  4. X if more than one return for a company is made at the same time (50).
  5. X if estimated figures are used in the returns (55).
  6. X if the company is a part of a group that is not small (60).
  7. X if the company needs to disclose the use of avoidance schemes or has been notified by an HMRC-monitored promoter (65).
  8. X if the company needs to adjust its profits or losses due to a transfer pricing adjustment for a UK-to-UK transaction with a connected business. The other business can make a compensating adjustment to align its profits and losses (70).
  9. X to confirm that your business is a small or medium-sized enterprise that is eligible for exemption from transfer pricing rules (75).
  10. X to indicate the submission of accounts for the period of the return (80) or to indicate a different period (85). If you are not submitting the accounts and iXBRL computations, explain the reasons in box 90.
  11. The total trading turnover from any source (145).
  12. X if the company is a bank, building society, insurance company, or other financial concern with no recognised turnover figure (150).
  13. The total of all trading profits in box 155 and the total of all losses in box 780 or 790.
  14. Unrelieved trading losses for earlier periods set against trade profits in box 155 (160).
  15. The company’s non-trading profits with respect to its loan relationships (170). The non-trading deficit from the loan deficit for the period is entered in box 795. Enter X in box 172 if the amount in box 170 includes carrying back a deficit from a later accounting period.
  16. The amount of annual payments not subject to Corporation Tax and from which Income Tax has not been deducted (175).
  17. The non-exempt dividends or distributions of a non-UK resident company (180).
  18. The gross amount before tax, excluding the amount in box 170 (185). A non-UK resident company landlord with tax withheld under the Non-residents Landlord Scheme should enter income in box 190 and tax withheld in box 515.
  19. Income from a property business (190).
  20. The non-trading gains on intangible fixed assets (195). A non-trading loss in boxes 265, 830, and 835.
  21. The tonnage tax profits from box F70 from supplementary page CT600F (200).
  22. Profits or gains not included under any other heading (205).
  23. The total gains in the period (210). Enter allowable losses for the period in box 825.
  24. Allowable losses, including losses brought forward (215). Make an entry only if you entered a figure in box 210.
  25. Amount of losses brought forward against certain investment income (225).
  26. Deficit carried forward from previous periods and offset against the non-trading profits of this period (230).
  27. Amount of loss on unquoted shares (240).
  28. Management expenses (245).
  29. Losses of a UK property business for the current or previous accounting period (250).
  30. Capital allowances for business management (255).
  31. Deficit of non-trading loan relationship against the profits of the same accounting period (260).
  32. Non-trade deficits from loan relationships carried forward against the profits of this accounting period (263).
  33. Trading losses of the current or a later accounting period (275).
  34. X if amounts carried back from later periods are included in box 275 (280).
  35. Total trading losses carried forward and settled against trading losses (285).
  36. Non-trade capital allowances (290).
  37. Qualifying donations to charities and community amateur sports clubs (305).
  38. Group relief claim (310).
  39. Group relief for carried forward losses (312).
  40. Amount of taxable total profits (315).
  41. Number of associated companies (326,327,328).
  42. X if the company is entitled to a small profit rate or marginal relief (329).
  43. Tax calculation (330 to 440).
  44. Community investment relief (445).
  45. Double taxation relief claimed against corporation tax (450).
  46. X in box 455 if box 450 includes an underlying rate relief claim.
  47. X in box 460 if box 450 includes the amount carried back from a later period.
  48. Advance corporation tax (465).
  49. Energy levies (986 and 987).
  50. Calculation of tax outstanding or overpaid (475 to 528).
  51. Research and developmental credit that was given in box L20 on the supplementary page CT600L Research and Development (530).
  52. Total of creatives tax credits (540).
  53. Land remediation tax credit (550).
  54. Life assurance company tax credit (555).
  55. Amount of first-year tax credit (565).
  56. Tax already paid and not repaid by HMRC (595).
  57. Group tax refunds surrendered to your company by another group company (610).
  58. Research and Development expenditure credits surrendered to your company by another group company (615).
  59. Optional exporter information (616 to 618).
  60. Exempt ABGH distributions that the company has received (620).
  61. Total number of companies in a 51% group, including your company (625).
  62. X if the company was a large company for quarterly instalments (630).
  63. X if the company was a very large company for quarterly instalments (631).
  64. X if the company is a part of the Group Payment Arrangement (635).
  65. X if the company has written down or sold intangible assets (640).
  66. X if the company has made cross-border royalty payments (645).
  67. Research and Development or creatives enhanced expenditure and tax reliefs (650 to 680).
  68. Land remediation enhanced expenditure (685).
  69. Capital allowances and balancing charges or disposal values (688 to 727).
  70. Allowances and charges are not included in trading profits and losses (733 to 752).
  71. Total expenditure on machinery and plant on which first-year allowance is claimed (760).
  72. Qualifying expenditure (760 to 775).
  73. Losses, deficits, and excess amounts (785 to 855).
  74. Complete box 860 if you do not want HMRC to make repayments less than a fixed amount.
  75. Complete boxes 900 to 915 if you want to surrender a tax refund to another group company.
  76. Repayment for the period covered by this return (865 to 895).


Bank Details

The quickest and safest option to receive a repayment is by a direct transfer from HMRC to your designated bank or Building Society account. If you are submitting numerous returns at the same time, make sure to include the account information on each.

  1. Name of the bank or building society of the person to be repaid (920).
  2. The 6-digit branch sort code of the person (925).
  3. Account number (930).
  4. Name of the account (935).
  5. Building society reference, if applicable (940).

Enter details in boxes 945 to 970 to nominate someone other than the company to receive a non-R&D credit repayment.



Every return must include a declaration:

  1. Name of the person making the declaration (975).
  2. The date on which the declaration is made (980).
  3. Status of the person making the declaration (985).



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