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 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, with three modes on the same Company Tax Return: Simple, a one-page form for micro-entity accounts; Advanced, the fuller guided form; and Full CT600, box by box. You can switch between them without re-entering anything, start a return for free and only pay when you file.

What is the guided ("simple") filing mode?

In guided mode you enter what you actually know — income, expenses, a balance sheet — and the software derives the tax. Taxley has two guided modes: Simple, a one-page form for micro-entity accounts, and Advanced, the fuller guided form with a live tax estimate. In either one:

• 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. In Taxley this is the Full CT600 view, and you can switch to it from Simple or Advanced without re-entering anything:

• 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, then switch to box-by-box if they want to inspect a figure; nothing needs re-entering.

If you're not sure your company suits self-filing at all, take the 30-second check to see whether Taxley fits.

Frequently asked questions

Do I lose my data if I switch approaches?

No, not in well-built software — both views should be windows onto the same return, so figures entered in one appear in the other. In Taxley you can switch between Simple, Advanced and Full CT600 at any time without re-entering anything.

Is box-by-box "more accurate"?

No — it's more controllable. The arithmetic is the same; box-by-box just exposes it, and any override of a calculated box is clearly flagged rather than silent. Accuracy still depends on the figures you put in, whichever mode you use.

Can software calculate everything for me?

No. Taxley calculates capital allowances, chargeable gains, group relief between UK companies, loss carry-back and a director's loan's section 455 tax for most cases, but it doesn't support R&D relief, terminal loss claims, consortium relief or overseas branches, or a bed-and-breakfasted director's loan unless it was repaid by a credited dividend, salary or bonus. For those, Taxley can't file yet.

Which CT600 filing mode should a first-timer use?

Start with a guided form — it asks for figures you already have and works the tax out. In Taxley that's Simple for most micro-entity returns, or Advanced for fuller small-company accounts or a mixed trading and property business. Switch to the box-by-box Full CT600 view only to inspect or override a specific CT600 box before filing.

Taxley offers three modes, switchable at any time on the same return: Simple, a one-page form that is the default for micro-entity returns of a trading or property company; Advanced, the fuller guided form with a live tax estimate, for example for FRS 102 small-company accounts or a mixed trading and property business; and Full CT600, a box-by-box editor with per-box validation and flagged overrides. Figures still deserve a qualified review before filing.