Trust & sourcing
Editorial policy
How we write our guides, where the facts come from, how we check and review them, and what we do when we get something wrong.
Why does Taxley publish guides?
We publish guides to explain, in plain English, the rules Taxley's software applies when it prepares and files UK Corporation Tax returns — so you can understand and sense-check your own return rather than take the numbers on trust. Each guide links to the official source behind its facts, so you can check them yourself.
Where do Taxley's facts come from?
Every statement of tax or company law in our guides comes from an official source (legislation, HMRC manuals, GOV.UK guidance or the Companies House register), and we link to it so you can check it yourself. When sources differ in authority, we rely on them in this order:
- Legislation — for example the Corporation Tax Acts 2009 and 2010 and the Companies Act 2006.
- HMRC manuals — for example the Company Taxation Manual, the Property Income Manual and the Corporate Finance Manual — for how HMRC applies the law.
- GOV.UK guidance — rates and allowances, deadlines, penalties and the Company Tax Return (CT600) guide.
- Companies House — the public register and its guidance on filing accounts.
For accounting questions we use the FRC's accounting standards (FRS 105 and FRS 102 Section 1A). We don't rely on secondary commentary — other software providers, forums or AI-generated answers — as the source for a tax fact.
How are figures in Taxley's guides dated and linked?
Every figure is dated and linked: we aim for every rate, threshold, penalty or deadline to say which financial year, tax year or filing date it applies to, and to link to the official page it comes from. For example, the £200 late-filing penalty applies to returns with a filing date on or after 1 April 2026.
Where a figure comes from a dated publication, such as HMRC's annual Corporation Tax statistics, we name the publication and its date so you can tell when it was current.
How are worked examples checked?
Each worked example is checked two ways before it is published: against Taxley's own Corporation Tax calculation engine, which uses the same rates table as the returns we prepare, and by recomputing it from the rule as GOV.UK states it. If the two checks disagree, the example isn't published until we know why.
For marginal relief, that means HMRC's published formula with the standard fraction of 3/200: a standalone company with £100,000 of profit in a 12-month period pays £25,000 at the 25% main rate, less £2,250 of marginal relief — £22,750 in total.
The parts of our engine that carry professional judgement — marginal relief, iXBRL tagging — are marked in the product for you to check, and they are the areas we most want you to check carefully before you file.
How are Taxley's guides structured?
Headings are phrased as the questions people actually ask ("What is a CT600?", "How does marginal relief work?"), and each one is answered directly in the first sentence beneath it — the detail follows, but the answer comes first. Every guide ends with a short FAQ, which keeps guides easy to skim and easy to quote accurately.
How often are Taxley's guides reviewed?
Money guides are re-checked against GOV.UK every quarter, rates and penalties every year on 1 April, and any guide an HMRC or Companies House change affects as soon as we become aware of it. Each guide shows when it was published or last updated, and that date moves only when the content changes.
- Money guides — any guide that states a price, rate, penalty or deadline — are re-checked against GOV.UK every quarter, in January, April, July and October.
- Rates and penalties are reviewed every year on 1 April, when the new financial year starts: Corporation Tax rates, thresholds and marginal relief, and the late-filing penalty schedule.
- When HMRC or Companies House announce a change, we update the guides it affects as soon as we become aware of it.
A review that finds nothing to change doesn't reset a guide's date. Guides that have been corrected or refreshed also list the main dated changes in an Update history at the end of the article.
Does Taxley use AI to write its guides?
Yes, for drafts. Drafts are prepared with AI writing tools. Nothing is published on that basis alone: every fact, figure and link is checked against the official sources above before publication, and the same corrections process applies whoever or whatever produced the first draft.
Who is responsible for the accuracy of Taxley's guides?
Guides carry a byline. Taxley UK LLP publishes the guides and is responsible for their accuracy. The byline doesn't change the standard: every fact, figure and link in a guide is checked against the official sources above before publication, and any correction follows the process below.
Are Taxley's guides tax advice?
No. Our guides are general information, not tax advice, and reading them does not create an adviser relationship. Rules change and your circumstances may differ. For anything beyond a straightforward case, such as terminal loss claims or R&D claims, we tell you plainly that Taxley can't file it yet.
How are mistakes in Taxley's guides corrected?
If you think something in a guide is wrong or out of date, email support@taxley.co.uk or use the contact page — we'd rather fix it than leave it. When we correct a guide, we fix the text, add a dated line to its update history and, for a correction of fact, add it to the log below.
We don't quietly rewrite a figure.
Corrections log
- Taxley's MTD service. MTD for landlords and four other Making Tax Digital guides said Taxley MTD handles digital records and quarterly updates and is free during beta. It isn't available yet. The guides now say so and point to HMRC's list of MTD-compatible software.
- HMRC's free filing service. How to file a CT600 yourself still described HMRC's own free online service as a way to file; it closed on 31 March 2026. The guide now says to use commercial software or an agent (paper only with a reasonable excuse or in Welsh), and the closure was added to What is a CT600, Dormant company tax return and Corporation Tax deadlines.
- Late-filing penalty. How to file a CT600 yourself gave the first late-filing penalty as £100. For returns with a filing date on or after 1 April 2026 it is £200.
- Property company interest. Corporation Tax for a property company treated mortgage interest as a property expense. A company gets relief for it under the loan relationship rules instead (HMRC manual PIM2052); the worked example now shows the right CT600 boxes.
- Instalment thresholds. Corporation Tax deadlines called companies with profits over £1.5 million "very large". They are "large" companies, which pay in quarterly instalments; "very large" companies have profits over £20 million and pay earlier.
- UTR and the CT603 notice. What is a UTR and How to file a CT600 yourself said the company UTR arrives on HMRC's first letters, such as the "Notice to deliver a Company Tax Return" (CT603). HMRC posts the UTR after the company registers; the CT603 is issued about a month after each accounting period ends (HMRC manual COM130130). A claim that the UTR sometimes carries a "K" suffix was replaced with an explanation of payment references.
- Internal research notes. MTD for landlords and Who has to use MTD for Income Tax contained wording from our internal research notes. It was replaced with the rules as GOV.UK states them: how non-resident landlords count property income, and the three-year opt-out.
- MTD penalty points. MTD penalties said points at the threshold reset after 24 months of on-time submissions. GOV.UK says 12 months, plus any outstanding submissions for the previous 24 months.
- Filing an estimate. What happens if you file your CT600 late suggested filing a best estimate on time and amending it later. We removed that advice: a careless inaccuracy in a return can itself be penalised.
- Marginal rate. Corporation Tax rates and marginal relief described 26.5% as an effective rate. It is the marginal rate on each extra pound of profit inside the band; the effective rate runs from 19% to 25%.
- Late-filing penalties. Corporation Tax deadlines gave the flat late-filing penalties as £100 each, rising to £500 for repeated lateness. For returns with a filing date on or after 1 April 2026 they are £200, rising to £1,000.
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