Simple vs box-by-box CT600 filing: which to use
In short: There are two honest ways software can help you prepare a Company Tax Return. A guided form asks for your accounts figures and works the tax out for you — fastest for a straightforward company. A box-by-box editor mirrors the actual CT600 so you (or your accountant) control every figure — better when your return has anything unusual. Good software lets you switch between the two without re-entering anything.
Taxley does exactly that: a Company Tax Return you can prepare in either mode, switchable on the same return. You can start one for free and only pay when you file.
What is the guided ("simple") filing mode?
You enter what you actually know — income, expenses, a balance sheet — and the software derives the tax:
- The Corporation Tax calculation (including the small profits rate, main rate and marginal relief) is applied for you.
- Totals and the tax estimate update as you type.
- Company details prefill from Companies House; last year's figures appear as comparatives.
- Anything genuinely specialist (capital allowances you're claiming, brought-forward losses, one-off adjustments) is a small optional section — you provide the figure, the software puts it in the right box.
Fits: most small companies with one trade or property business and a clean year.
What is the box-by-box ("Full CT600") mode?
Instead of a questionnaire, you see the return itself — sections and box numbers matching the official CT600 form — with validation as you go:
- Calculated boxes show the engine's figure; you can override any of them with your own (clearly flagged, never silent).
- Errors and warnings appear against specific boxes ("complete box 326 or 327/328") rather than as a wall at the start.
- It reads like the form your accountant files, which makes an accountant's review of your draft much easier.
Fits: returns with figures prepared elsewhere, accountants checking a client's draft, or anyone who wants to see exactly what will be filed.
Which should you choose?
Use the guided ("simple") mode for a straightforward company where you just want to enter your figures and file; use box-by-box ("Full CT600") when you need to see or set specific CT600 boxes. Most people should start with guided.
| Your situation | Better fit |
|---|---|
| Straightforward year, you have the accounts figures | Simple |
| An accountant gave you computed figures to file | Comprehensive |
| You want to check what the software derived | Start Simple, switch to Comprehensive to inspect |
| Chargeable gains, R&D, director-loan tax | Neither alone — those need an accountant's input |
Frequently asked questions
Do I lose my data if I switch approaches?
Not in well-built software — both views should be windows onto the same return, so figures entered in one appear in the other.
Is box-by-box "more accurate"?
No — it's more controllable. The arithmetic is the same; box-by-box just exposes it. Accuracy still depends on the figures you put in.
Can software calculate everything for me?
No honest software claims that. Capital allowances, chargeable gains and reliefs like R&D depend on facts and judgement — tools can place your figures correctly, but a qualified accountant should produce or review them.
Which CT600 filing mode should a first-timer use?
Start with the guided (simple) form — it asks for figures you already have and works the tax out. Switch to the box-by-box view only if you want to inspect or override a specific CT600 box before filing.
Taxley offers both: a one-page guided form with a live tax estimate, and a "Full CT600" box-by-box editor with per-box validation and flagged overrides — switchable at any time on the same return. Figures still deserve a qualified review before filing.
People also ask
Keep reading
Prepare your CT600 with Taxley
Enter your figures and get a CT600 plus FRS 105 / FRS 102 iXBRL accounts and computations, ready to file. See your Corporation Tax before you pay — and you only pay when you file.
Start your return