Company accounts, tax computation and CT600 filing
Corporation Tax Accountant in Cardiff
We turn the company's accounts into a supported Corporation Tax computation, resolve the adjustments behind the figure and prepare the CT600 for your approval before it is filed with HMRC.
For owner-managed companies, consultants, contractors, property companies, trades, retailers, hospitality businesses and growing teams across Cardiff and South East Wales.
Start with the full company position
When should a Corporation Tax accountant review the year?
The return needs more than a profit figure whenever the accounts contain capital purchases, director transactions, losses, investment income, property activity or connected companies. Those items should be settled before the CT600 is approved.
Read the official Company Tax Return overview ↗The company has its first accounts and possibly two tax periods
A first set of statutory accounts can cover more than 12 months, while a Corporation Tax accounting period cannot.
Salary, dividends, expenses or loans need reconciling
Personal withdrawals must agree with payroll, dividend paperwork, expense claims and the director's loan account.
Equipment, vehicles, software or premises were acquired
Accounting depreciation is replaced by the appropriate tax treatment, which may include capital allowances.
The owners control another company
Associated companies can reduce the Corporation Tax profit limits and change the marginal-relief calculation.
The company made a loss, sold an asset or stopped trading
The period, available claims and interaction with earlier or future profits need to be established.
A return is late or HMRC has issued a determination
The actual return still needs preparing so that the liability, interest and penalties can be recalculated.
Accounts to submission
What our Corporation Tax return service includes
The exact scope follows the condition of the records. Where statutory accounts are included, they and the tax return are prepared as one connected year-end process.
Period and filing review
We confirm the accounting period, notice to file, payment date, CT600 deadline and Companies House accounts date.
Accounts and balance-sheet checks
The trial balance, bank, debtors, creditors, fixed assets, payroll, VAT and director balances are reviewed for year-end completeness.
Corporation Tax computation
Accounting profit is adjusted for disallowable costs, capital items, allowances, other income, chargeable gains and reliefs.
Rate and associated-company check
We establish the applicable rate, adjusted profit limits and marginal relief rather than applying one percentage automatically.
CT600 and supporting documents
The return, computation, iXBRL accounts and any relevant supplementary pages are assembled for review.
Approval, filing and payment details
You see the final liability and key assumptions before filing, followed by submission confirmation and the period-specific payment reference.
You receive the approved tax calculation, filed CT600, supporting computation, submission receipt and payment instructions.
How the fee is scoped →The accounts-to-tax bridge
Corporation Tax is calculated from taxable profit, not the accounts figure alone
The computation explains every material movement from profit before tax to taxable total profits. It should let a director see why the tax result differs from the financial accounts.
The exact order depends on the company's activities, but the bridge normally follows these stages.
- StartAccounting profit before taxAgreed to the final statutory accounts.
- AddExpenses not deductible for taxSuch as depreciation, client entertaining and private or non-business costs.
- DeductCapital allowances and eligible deductionsBased on asset type, date, use and available allowance.
- IncludeOther taxable income and chargeable gainsProperty, interest, investments and company asset disposals where relevant.
- ApplyLosses, reliefs and associated-company limitsClaims are made only where the facts and supporting records permit.
- ResultCorporation Tax liabilityAt the applicable rate, including marginal relief where due.
Rates for non-ring-fence profits
Small profits rate, main rate and marginal relief
For the financial year beginning 1 April 2026, the small profits rate is 19% where profits are £50,000 or less, and the main rate is 25% where profits exceed £250,000. Marginal relief can reduce the effective charge between those limits.
The £50,000 and £250,000 limits are reduced for short accounting periods and divided by the total number of associated companies. A company's rate therefore cannot always be inferred from its own profit alone.
Check current Corporation Tax rates and limits ↗Small profits rate, subject to adjusted limits and company circumstances.
A calculation produces a gradual rise in the effective rate.
Main Corporation Tax rate, subject to the relevant rules.
Thresholds shown are the standard 12-month limits before adjustment for associated companies.
Three dates, two authorities
Corporation Tax, CT600 and Companies House deadlines
The payment date usually arrives before the CT600 filing date. Companies House accounts follow a separate legal timetable, so one submission does not replace another.
Close the accounting records
Reconcile transactions and collect the evidence needed for the accounts and computation.
File private company accounts
The normal annual deadline is nine months after the financial year ends. First accounts normally have a 21-month incorporation deadline.
Pay Corporation Tax
This usual deadline applies to taxable profits up to £1.5 million; larger companies may pay by instalments and related companies can affect the limit.
File the Company Tax Return
The CT600 and supporting documents are normally due 12 months after the accounting period ends.
Filing change from 1 April 2026
Company Tax Returns now require commercial software
The joint HMRC and Companies House online accounts and Company Tax Return service closed on 31 March 2026. From 1 April 2026, a Company Tax Return must be filed with HMRC using commercial software.
That filing package normally includes the CT600, tax computation and accounts in the required iXBRL format. Software transmits the documents; it does not decide whether the underlying accounting and tax treatment is correct.
Read the official service closure notice ↗Different records create different risks
Corporation Tax returns for Cardiff companies
We scope the return around how the company earns, spends and extracts money. The same CT600 form can sit behind very different trading patterns.
Consultants, contractors, agencies and practices
Accrued income, work in progress, homeworking, travel, pension contributions and director remuneration need to agree across the accounts and payroll.
Trades, subcontractors and construction companies
CIS deductions suffered, retentions, work in progress, vans, tools, subcontractors and VAT balances need year-end reconciliation.
Property investment and development companies
Rental income, loan interest, capital improvements, service charges and sales must be classified according to the company's actual activity.
Software, creative, ecommerce and online businesses
Platform settlements, overseas services, development costs, subscriptions, stock and intellectual property can cross several tax treatments.
Retail, hospitality and local service companies
Card, till and delivery-platform income should reconcile to gross sales, with payroll, stock, tips, deposits and VAT treated consistently.
Groups and commonly controlled companies
Associated-company limits, intercompany balances, management charges, group relief and transactions between connected parties require a joined-up review.
The company and director are separate
Salary, dividends, expenses and director loans must agree
Money leaving an owner-managed company is not automatically a dividend or deductible expense. Each payment should have the correct legal, accounting, payroll and tax treatment.
An overdrawn director's loan account can create a company tax charge and a benefit-in-kind issue. A later repayment may permit relief, but the timing and anti-avoidance rules need checking.
Check the official director's loan overview ↗Must run through payroll and be supported by the employment and payment records.
Require sufficient distributable reserves, the proper decision and dividend documentation.
Need a genuine company purpose and evidence; private costs can create loan or benefit consequences.
Withdrawals and repayments are tracked separately from salary, dividends and expense reimbursements.
Cars, medical cover, cheap loans and other benefits may require payroll or P11D treatment.
Salary, dividends, benefits and loan write-offs may also affect the director's Self Assessment.
Self Assessment service →Accounting cost does not always equal tax deduction
Company expenses, capital costs and disallowable items
We look at why the company incurred the cost, what it acquired and how it was used. The invoice description or bookkeeping code alone is not enough.
- Staff costs and employer contributions
- Premises, insurance and professional fees
- Business travel and subsistence within the rules
- Routine software, advertising and operating costs
- Employer pension contributions when paid and allowable
- Equipment, vehicles, premises and improvements
- Mixed business and private expenditure
- Loan interest and finance arrangements
- Software development and intangible assets
- Stock, work in progress and provisions
- Depreciation added back before capital allowances
- Client entertaining generally disallowed
- Fines and penalties generally disallowed
- Dividends and Corporation Tax not business expenses
- Unsupported or personal director costs
Claims follow evidence
Capital allowances, losses and company tax reliefs
A relief is considered because the facts support it—not added as a generic year-end adjustment. Elections, time limits and future use of losses can matter as much as the immediate tax figure.
Plant, machinery, vehicles and certain building expenditure are classified by asset, date and use before a claim is chosen.
Current-period, carry-back, carry-forward and group options are compared with the company's circumstances and claim deadlines.
Company disposals can require indexed historic cost, capital-loss and relief analysis inside the Corporation Tax computation.
Any R&D claim requires a qualifying-project, cost and notification review; ordinary product improvement is not labelled as R&D without evidence.
Qualifying company donations can be deductible under their own rules and should not be confused with sponsorship or staff fundraising.
Ownership, periods, available losses and claims between group companies are checked together.
A clean handover shortens the review
Records needed for company accounts and the CT600
We confirm the final list after understanding the company. Secure digital copies are normally sufficient, and incomplete records can be assessed before a fee is agreed.
Bookkeeping export or trial balance, all business bank and card statements, sales, purchases, finance and VAT records.
Debtors, creditors, stock, work in progress, accruals, prepayments, fixed assets and finance balances.
Payroll, expense claims, dividend minutes and vouchers, benefits, withdrawals, repayments and money introduced.
UTR, HMRC notices, prior accounts and CT600, loss schedules, capital-allowance pools and payments on account.
Asset purchases or sales, property transactions, grants, overseas income, investments, related parties and legal agreements.
A visible route to filing
How we prepare a Company Tax Return
Questions are raised while the records are being reviewed, not after a return has been submitted. You retain the approval decision.
- 01
Scope and deadlines
We establish the entities, periods, records, accounts work, filing dates and unusual events before confirming the fee.
- 02
Reconcile the accounts
Balance-sheet controls and key income and expense streams are reviewed; missing information is listed clearly.
- 03
Prepare the tax computation
Adjustments, capital allowances, losses, reliefs, rates and associated companies are calculated and documented.
- 04
Director review and approval
We explain the liability, payment date and material judgments, then obtain approval for the accounts and CT600.
- 05
File and close the year
The return is filed through commercial software and confirmation, payment details and outstanding actions are provided.
Do not leave an estimate unchallenged
Late CT600 returns and HMRC determinations
For returns with a filing date on or after 1 April 2026, the fixed penalty is £200 when late and another £200 once the return is more than three months late. Higher £1,000 amounts apply after repeated failures.
At six months HMRC can estimate the tax and add 10% of unpaid tax; another 10% can arise at 12 months. A determination cannot be appealed, but filing the actual Company Tax Return replaces the estimate and lets HMRC recalculate the position.
Check current late Company Tax Return penalties ↗Fixed late-filing penalty.
Second fixed penalty.
HMRC determination plus 10% of unpaid tax.
A further tax-related penalty.
A quote based on the actual year
Corporation Tax accountant fees
The fee is agreed after we understand the accounts scope, bookkeeping condition, transactions, deadlines and any earlier-year issues. A clean CT600 from final accounts should not be priced like reconstructed accounts with an HMRC determination.
Ask for a fixed quoteAccounts work
Whether statutory accounts are included, already final or need correction.
Record condition
Reconciled bookkeeping versus missing statements, control differences or reconstructed records.
Tax complexity
Assets, property, gains, losses, reliefs, associated companies and director transactions.
Timing and HMRC position
Normal annual work versus overdue periods, determinations, penalties or enquiry correspondence.
Direct answers for company directors
Corporation Tax return questions
These answers cover the points most often needed before the work can be scoped.
When is Corporation Tax due?+
A company with taxable profits up to £1.5 million normally pays Corporation Tax nine months and one day after the accounting period ends. Larger companies can have instalment-payment dates, and related companies can affect the £1.5 million threshold. The exact date should be confirmed for the company.
When is the CT600 Company Tax Return due?+
The usual filing deadline is 12 months after the end of the Corporation Tax accounting period. Payment normally falls earlier. If HMRC issues a notice to deliver a return, it may still need filing when the company made a loss or has no Corporation Tax to pay.
Can the accounts profit be multiplied by 19% or 25%?+
Not reliably. Accounting profit can require adjustments for depreciation, disallowable expenditure, capital allowances, other income, chargeable gains, losses and reliefs. The rate can also depend on augmented profits, period length and associated companies.
What is Corporation Tax marginal relief?+
Marginal relief reduces the Corporation Tax charge for qualifying companies whose standard 12-month profits fall between £50,000 and £250,000. Those limits are shortened for shorter periods and divided by the number of associated companies.
Do dormant or loss-making companies file a CT600?+
A genuinely dormant company does not normally pay Corporation Tax, but the Companies House accounts obligation remains. If HMRC has issued a notice to file, a Company Tax Return should be submitted unless HMRC withdraws the notice. A loss-making trading company may still need to file and make a loss claim.
Can you prepare the company accounts and CT600 together?+
Yes, where agreed in the scope. Preparing the statutory accounts, tax computation and CT600 together helps keep the balance sheet, profit, director transactions and tax disclosures consistent. We confirm what bookkeeping or accounts work is included before starting.
What happens if a director owes money to the company?+
The balance remains on the director's loan account. Depending on the amount, shareholder status, repayment date and interest, the company can face a temporary Corporation Tax charge and reporting duties, while the director may have a benefit-in-kind or personal tax consequence.
Can a late Corporation Tax return still be corrected?+
Yes. The records and actual tax position should be reconstructed and the outstanding return filed. If HMRC has made a determination, the filed return replaces the estimate. Penalties, interest and any appeal or disclosure position then need separate review.
Can I file a CT600 directly on the old HMRC service?+
No. The joint HMRC and Companies House online filing service closed on 31 March 2026. From 1 April 2026, Company Tax Returns must be filed with HMRC using commercial software.
Before the payment date arrives
Get the accounts and Corporation Tax position working from the same records
Tell us the company year end, filing deadline and current bookkeeping position. We will identify the work required and give you a clear scope before anything begins.
Corporation Tax information reviewed 3 September 2026. Tax treatment depends on the company's facts, accounting period and current law.