Guides

How do I register my company for Corporation Tax?

The one step that's yours: telling HMRC your company is active within 3 months of starting to trade.

What is Corporation Tax and how does it work?

The plain-English starting point: what the tax is, whether your company owes it, and the yearly cycle.

What is a UTR (your company's tax reference)?

The 10-digit number HMRC uses for your company: where it comes from, where to find it, and what it is for.

How is Corporation Tax worked out? (from your profit to your tax bill)

A real worked example in pounds: your accounts profit, the tax adjustments, then the rate.

Do I pay Corporation Tax if my company made no profit (or a loss)?

No profit means no tax, but you still file, and a loss can cut a future bill.

What's the Corporation Tax rate for a small company?

The two main rates, the band in between, and what marginal relief means for you.

Marginal relief explained (the 19% to 25% taper)

Why profit between £50,000 and £250,000 slides up from 19% toward 25%, with a worked example.

Trading losses: carrying them back and forward

How a loss cuts your tax: use it this year, carry it back for a refund, or carry it forward.

Associated companies: how they change your tax bands

Why controlling more than one company shrinks your £50k and £250k limits and can push up your rate.

What records do I need to keep for Corporation Tax?

What to keep, the six-year rule from your year-end, and the £3,000 fine if you don't.

Companies House vs HMRC: what's the difference and what do I send each?

Two bodies, two filings: accounts and a confirmation statement to one, your tax return to the other.

What expenses can my company claim against Corporation Tax?

Which business costs cut your tax, the bits people get wrong, and what we sort for you.

Can I claim my laptop, van or equipment?

Capital allowances and the £1m Annual Investment Allowance, with no jargon.

What can't my company claim? (disallowable costs)

The costs the company can pay but that don't cut your tax: entertaining, fines, dividends and more.

Can my company claim travel, mileage and parking?

Work travel and driving your own car at 55p a mile, the commute trap, and why fines never count.

Can my company claim working-from-home costs?

The safe £6 a week, and the household-bill mistake that lands you a personal tax bill.

Can my company claim my mobile phone and broadband?

One company-name phone is tax-free, and the personal-contract trap that costs you tax.

Can my company claim food, drink and entertaining?

Client lunches the company can pay but don't cut tax, your everyday lunch is out, and a staff do does.

Every Corporation Tax deadline (and what happens if you are late)

The 9-month, 12-month and 9-months-and-a-day rules, and the exact late fines.

Paying Corporation Tax late: interest and what to do

How HMRC interest builds up daily, why paying late differs from filing late, and time to pay.

Corporation Tax penalties and how to appeal

The exact late-filing fines, £200 day one, 10% at 6 and 12 months, and how to appeal one.

What happens if HMRC checks your Corporation Tax (a compliance check)?

What a compliance check is, how far back HMRC can go, and how good records protect you.

Companies House late-accounts penalties: the exact amounts

The exact fine for filing your accounts late: £150, then £375, £750 and £1,500, and when it doubles.

How do I file my Company Tax Return?

The five steps start to finish: accounts, the tax, the CT600, sending it to HMRC, and paying.

What is a CT600, and do I need to file one?

What the CT600 form is, and whether your company has to send one.

What it costs to file yourself vs an accountant

Software vs an accountant: what each price actually buys, and the £200 cost of deciding nothing.

What is iXBRL tagging, and why does HMRC want it?

What iXBRL is, why HMRC asks for it, and why you don't do it by hand.

How to amend your Company Tax Return if you got something wrong

For about a year after the deadline you resend corrected figures, and HMRC squares up the tax.

Is it safe to file my own Corporation Tax?

Yes, you can file it yourself, no accountant required. The three parts that go wrong, and how software does them.

Getting set up to file your own Corporation Tax

The one-off admin every new director needs first: telling HMRC, your UTR, Government Gateway, your Companies House code and the key dates.

What are boxes 30 and 35 on the CT600? (your accounting period)

The two date boxes that start the return, why they match your accounts year, and the two-return first year.

What is box 145 on the CT600? (turnover)

Your trading sales only: why loans, grants, bank interest and rent never belong in the turnover box.

What is box 155 on the CT600? (trading profits)

The tax version of your profit: depreciation and client entertaining added back, capital allowances taken off.

What is box 165 on the CT600? (net trading profits)

Box 155 minus box 160: how old losses shrink this year's profit, and why box 165 can never be negative.

What is box 190 on the CT600? (property income)

Where rent goes on the return: the letting profit, the allowable costs, and why rent is never turnover.

What is box 235 on the CT600? (and where trading losses actually go)

The running total of all your company's income, and why a loss year goes in box 780, not here.

What is box 315 on the CT600? (profits chargeable to Corporation Tax)

Your final taxable profit: every income strand added up, every deduction off, and the number that picks your rate.

What are boxes 380 to 395 on the CT600? (rates and marginal relief)

The profit, rate and tax grid: financial years, 19% or 25%, and where marginal relief actually lives.

What are boxes 435 and 440 on the CT600? (Corporation Tax chargeable)

The marginal relief discount and the bill it leaves: box 430 minus box 435 equals your Corporation Tax chargeable.

What is box 475 on the CT600? (the tax you owe)

Your net Corporation Tax bill, the 9-months-and-1-day payment deadline, and the 17-character reference.

Do I need to file a Company Tax Return?

A plain yes or no, whether you made a loss, earned nothing, or are dormant.

My company is dormant, what (if anything) do I file?

What a dormant company actually has to send, and to whom, and why it never means file nothing.

What's a director's loan, and why does it affect my tax?

The overdrawn director's loan account, the 33.75% charge, and the £10,000 trap, explained simply.

First year of trading: what your first return covers

Your first year, why it runs past 12 months, and the two-return quirk that catches new companies out.

How do I change my company's accounting period (year-end)?

The shorten and lengthen rules, what it does to your deadlines, and the two-return split.

Paying yourself: salary, dividends and the company tax angle

How a salary cuts your company's tax, why a dividend doesn't, and what the right mix depends on.

Closing or striking off your company: what about Corporation Tax?

The final return, the last tax bill, and telling HMRC, the three tax jobs before you can strike it off.

My company rents out property: how is that taxed?

Corporation Tax on the rental profit, mortgage interest taken off in full, and a worked example.

Company Tax Returns for contractors and freelancers

Filing for a one-person limited company: salary vs dividends, expenses, the director's loan trap and deadlines.

Sole trader to limited company: what changes when you incorporate

What ends, what starts, and what an accountant still handles when you go from sole trader to a limited company.

You set up a company but kept paying yourself like a sole trader

Why money you drew from the company is a director's loan, and the steps to put it right before it costs you tax.

What is FRS 105? Micro-entity accounts in plain English

The simplest accounting standard for the smallest companies, and what goes in the accounts.

Does my company count as a micro-entity?

The size tests with £ thresholds, so you can tell if you qualify.

FRS 105 vs FRS 102: which one is my company?

Which accounting rules you use comes down to size: micro-entities use FRS 105, small companies FRS 102.

HMRC error 1046: why your sign-in was refused and how to fix it

Why HMRC refused your submission with error 1046, the four causes, and the fix for each one.

How to switch on Corporation Tax in your Government Gateway (and enter the activation code)

Adding Corporation Tax to your business tax account, and what to do with the activation code letter.

Lost your Government Gateway user ID or password? Here's how to get back in

Recovering a lost user ID or password online, locked accounts, dead email addresses and lost phones.

Where do I find my Companies House authentication code?

What the 6-character code is, where the letter went, and how to request a new one in time.

Where do I find my company's UTR (the 10-digit tax reference)?

Which HMRC letters show your 10-digit UTR, and how to get a copy posted if you cannot find one.

My company accounts are overdue. What do I do today?

How bad it really is, the exact penalty bands, why filing fast beats appealing, and what you need to file today.

The free HMRC filing service has closed. What are your options?

What closed on 31 March 2026, what has not changed, and your two real routes: software or an accountant.

Can I still file my company tax return myself in 2026?

Yes. Self-filing is still one of the two routes HMRC describes; only the tool changed. Who it suits, and what you need.

What does HMRC-recognised software actually mean?

Recognition is HMRC's shopping list, not a review score: what the list does and does not tell you, and the five checks that matter.

Company tax returns for contractors

Billing day rates through your own company: the CT600 you must file, the costs that count, and where IR35 belongs.

Company tax returns for online sellers

What online sellers must file, what they can claim, and why the platform payout is not your turnover once fees come off.

Company tax returns for tradespeople

The van, tools, materials and safety kit a trade company can claim, plus the CIS deduction trap to check before you file.

Company tax returns for cleaning businesses

What a small cleaning company must file, what it can claim on products, kit and travel, and the one-account trap to avoid.

Company tax returns for photographers and videographers

Shoot fees, licensing and stock royalties as income, cameras and kit as capital allowances, and the deadlines you cannot miss.

Company tax returns for personal trainers

Filing for a personal trainer's limited company: what counts as income including cash sessions, and the costs your company can claim.

Company tax returns for hairdressers and beauty businesses

The hair and beauty version: card and cash takings, product and kit costs, and the chair rental trap that muddles whose money is whose.

Company tax returns for couriers and delivery drivers

What counts as platform income, the car-versus-van rules, mileage at 55p, and filing both returns without an accountant.

Company tax returns for consultants and freelancers

Company Tax Returns for consultants and freelancers: what your company files, which costs count, and where your dividends sit.

Company tax returns for cafés and food businesses

What your Company Tax Return and Companies House accounts look like for a small café, coffee shop, takeaway or caterer.

Company tax returns for property investment companies

What a property company files, why the rent is company income taxed on the profit, and how a company beats a personal landlord on mortgage interest.

Company tax returns for IT and software companies

What an IT or software company files, why a card or subscription payout is not your turnover, and how to claim cloud, kit and equipment.

Company tax returns for marketing and creative agencies

What a marketing, design or PR agency files, and the recharged client ad spend trap that inflates turnover but not the tax.

Company tax returns for construction companies

What a construction company files, the materials-billed-on and plant hire-versus-buy rules, and where CIS and the VAT reverse charge need an accountant.

Company tax returns for private therapists and healthcare practitioners

What a private therapy or clinic company files, why insurer payments are income, and the VAT exemption that makes health work different.

Company tax returns for recruitment agencies

What a recruitment or staffing agency files, why the whole temp invoice is income but only the margin is taxed, and where temp payroll needs an accountant.

Company tax returns for tutors and education businesses

What a tutoring or education company files, why cash and platform lesson fees are all income, and which teaching costs and courses count.

Company tax returns for driving instructors

What a limited-company driving school files, why lesson fees are simple income, and the tuition-car trap that turns a company car into a taxed perk.

Company tax returns for mechanics and garages

What a garage or mobile mechanic files, why parts billed on go in gross as both income and cost, and the company-van trap to watch.

Company tax returns for dog groomers and pet services

What a grooming, walking or boarding company files, why cash and app payouts are all income, and how to claim kit, the van and licensing.