Tax Filing · United KingdomYour UK returns come from the same books but run on different calendars. We file them so the numbers agree.
We prepare and file Company Tax Returns, Self Assessment and partnership returns, VAT returns and Making Tax Digital quarterly updates for UK businesses and their owners.
Tax
At a glance
- Authorities
- HM Revenue & Customs (HMRC)
- Forms & references
- CT600SA100SA103SA800VAT return (MTD)
- Filed with
- HMRC
- Company Tax Return
- CT600, due 12 months after the period ends
- Self Assessment
- Online by 31 January after the tax year
- VAT returns
- Usually 1 month and 7 days after the VAT period
Overview
What it is, and why it matters.
A limited company files a Company Tax Return (CT600) with its accounts and tax computations in iXBRL format, due 12 months after the end of its accounting period. The Corporation Tax itself is usually due earlier, 9 months and 1 day after the period ends.
Sole traders, partners, landlords and many company directors file a Self Assessment return (SA100) for the tax year to 5 April, online by the following 31 January. Partnerships and LLPs also file a partnership return (SA800).
VAT-registered businesses file through Making Tax Digital software, usually quarterly. Since 6 April 2026, sole traders and landlords with qualifying income over £50,000 also send quarterly updates under MTD for Income Tax. At the time of writing, that threshold falls to £30,000 from April 2027 and £20,000 from April 2028.
Late returns and late payments bring penalties and interest. For VAT, and for anyone within MTD for Income Tax, late submissions build up penalty points before a financial penalty is charged.
Who needs it
Who typically needs it.
- 01
Owner-managed companies
Companies that want the CT600, the accounts and the directors’ Self Assessment prepared from one set of figures.
- 02
Sole traders and landlords in MTD
People now sending quarterly updates under Making Tax Digital for Income Tax, or who will from April 2027.
- 03
Partnerships and LLPs
Firms filing an SA800 and needing each partner’s share of profit carried correctly onto their own return.
- 04
VAT-registered businesses
Businesses that want each VAT return checked against the books before it goes to HMRC.
- 05
Businesses behind on filings
Companies and individuals with late returns, HMRC determinations or a pile of penalty notices.
When you need it
The moments that usually trigger it.
- Your company’s year end has passed and the 9-month payment date is coming up.
- You’ve received a notice to deliver a Company Tax Return (CT603) from HMRC.
- The 31 January Self Assessment deadline is approaching and your records aren’t ready.
- Your self-employment or property income puts you in MTD for Income Tax, and quarterly updates are now due.
- A VAT return is due and your bookkeeping and VAT account don’t agree.
- HMRC has issued penalties, a determination or a compliance check letter.
Scope
Exactly what we handle.
Our engagement letter lists these specifically, so you know what is included before any work begins.
- 01
Corporation Tax computations, capital allowances and CT600 filing with iXBRL-tagged accounts and computations.
- 02
Working out Corporation Tax payments and dates, including quarterly instalments for large companies.
- 03
Self Assessment returns for sole traders, directors, partners and landlords, including dividends and payments on account.
- 04
Partnership returns (SA800) and each partner’s profit share.
- 05
VAT returns under Making Tax Digital, reconciled to your ledgers before submission.
- 06
Quarterly updates and the year-end return under MTD for Income Tax.
- 07
Catching up on late returns, appealing penalties where there is a reasonable excuse and discussing Time to Pay with HMRC.
- 08
Replying to HMRC letters and queries about the returns we file.
The process
How it runs, step by step.
Timings depend on the authority and on how quickly documents come together. We tell you what’s typical for your case at the start.
Start with a conversationRecords in
You send your bookkeeping, bank statements and supporting documents, or give us access to your accounting software.
Review and reconcile
We check the figures against bank and VAT records and raise questions before anything is calculated.
Prepare
We prepare the computations and returns, and explain what tax is due and when it has to be paid.
Approve
You review and approve each return. Nothing is filed without your sign-off.
File and diarise
We submit to HMRC, keep the acknowledgements and set reminders for payments, payments on account and the next filing.
What we’ll need
The information to have ready.
A typical checklist. After the first conversation we send a version specific to your situation, so you don’t gather anything you don’t need.
Companies
- Bookkeeping records or a trial balance for the period
- Bank statements for every account
- Asset purchases and disposals
- Director’s loan account movements and dividends declared
- Last year’s accounts and CT600
Individuals
- P60, P45 or payslips and any P11D
- Dividend statements and interest received
- Self-employment and rental income and costs
- Pension contributions and Gift Aid donations
- Your UTR and National Insurance number
VAT
- Sales and purchase invoices for the period
- The VAT account from your software
- Postponed import VAT statements, if you import goods
Partnerships
- The partnership agreement or profit-sharing ratios
- Each partner’s UTR
- Partnership accounts for the period
Please don’t email passports or bank statements. Once we’ve spoken, you’ll get access to a secure upload.
Common mistakes
Where this usually goes wrong.
The problems we are most often asked to fix, and what they tend to cost.
- Mistake 01
Treating the return deadline as the payment date
For most companies, Corporation Tax is due 3 months before the CT600 deadline. Paying when the return is filed means interest has already been running.
- Mistake 02
Forgetting payments on account
Where a Self Assessment bill is over £1,000 and most of it wasn’t taxed at source, HMRC usually expects advance payments towards next year, so a first January bill can be much larger than expected.
- Mistake 03
Returns that don’t reconcile
VAT returns, accounts and a CT600 that tell different stories are an easy prompt for HMRC questions.
- Mistake 04
Leaving a director’s loan overdrawn
Money owed to the company by a director that isn’t repaid within 9 months of the year end can trigger a temporary extra Corporation Tax charge under section 455.
- Mistake 05
Ignoring MTD for Income Tax
Anyone over the threshold needs compatible software and digital records. Carrying on with paper records and a single annual return is no longer enough.
Worth knowing
The limits, stated upfront.
We work from the records you provide. We review them but don’t audit them.
HMRC enquiries and compliance checks can take time, and the outcome rests with HMRC.
R&D tax relief claims, personal residence questions and group reorganisations are scoped separately.
Penalty appeals succeed only where there is a reasonable excuse or HMRC has made an error. We can’t promise a penalty will be cancelled.
Questions
Tax Filing: frequently asked.
If yours isn’t here, ask us directly. We’ll answer in plain terms.
Ask a questionWhen is my company’s Corporation Tax due?
Usually 9 months and 1 day after the end of the accounting period, which is before the CT600 filing deadline of 12 months. Large companies pay in quarterly instalments instead.
Why does HMRC need accounts in iXBRL?
HMRC requires the accounts and tax computations sent with a CT600 to be tagged in iXBRL, a machine-readable format. We prepare them in software that produces the tagging.
What are payments on account?
Advance payments towards the next Self Assessment bill, due on 31 January and 31 July, each usually half of the previous year’s bill. They apply when that bill was over £1,000, unless most of your tax was already collected at source.
Am I in Making Tax Digital for Income Tax?
You are if you are a sole trader or landlord whose qualifying income (turnover plus gross rents) was over £50,000 in 2024–25. At the time of writing, the threshold falls to £30,000 from April 2027 and £20,000 from April 2028, and partnerships are not yet included.
What happens if I file late?
It depends on the tax. Late Company Tax Returns and Self Assessment returns outside MTD draw a fixed penalty straight away that grows the longer they are late; VAT and MTD for Income Tax use penalty points, and late payment brings interest and further penalties.
Can you catch up on returns from previous years?
Yes. We rebuild the figures from bank records where needed, file the outstanding returns and, where it helps, speak to HMRC about penalties and Time to Pay.
Do you file the accounts at Companies House too?
Statutory accounts for Companies House are part of our Financial Statements & Reporting service. We usually prepare them alongside the CT600 so the two match.
Related
Often needed alongside this.
The equivalent in our other countries
Speak with a consultant
Talk to us about tax Filing.
Pick the closest match and we’ll take it from there. You’ll get a written scope and fee before any work begins.
Or use our three-step guide, or email hello@fiscorra.com
