CT600 preparation in AccBooks AI

What is the CT600?

The CT600 is the UK company tax return — the official form you submit to HMRC reporting your profits, tax adjustments and corporation tax liability for each accounting period. It must be filed within 12 months of your accounting period end.

Since 2010, all CT600s must be filed online in iXBRL format. AccBooks generates an iXBRL-tagged CT600 ready for submission.

Starting a CT600 in AccBooks

1. Go to Corporation tax → CT600 preparation.
2. AccBooks shows a list of accounting periods. Click Prepare on the period you want to file.
3. AccBooks pulls your accounting profit from the P&L, applies automatic adjustments and presents the draft tax computation.

The tax computation

The computation starts with your accounting profit and applies adjustments to arrive at taxable profit:

Item	Notes
Accounting profit	From your P&L for the period
+ Depreciation	Added back — not deductible for tax
− Capital allowances	Annual Investment Allowance, Writing Down Allowance
+ Disallowable expenses	Client entertaining, fines, non-trade losses
+ Loan relationship debits	Non-trading deficits carried forward
− Qualifying charitable donations	Gift Aid donations made in the period
− R&D enhanced deduction	If R&D relief applies
= Taxable profit	The figure tax is calculated on

AccBooks populates most lines automatically. Review each line and add any items not captured automatically.

Capital allowances

AccBooks calculates capital allowances from your fixed asset register automatically. Go to Fixed assets → Capital allowances to review the calculation by pool:

• Main pool (18% WDA) — most plant and machinery.
• Special rate pool (6% WDA) — integral features, long-life assets.
• Annual Investment Allowance (AIA) — 100% relief in the year of purchase, up to £1 million.
• First Year Allowances (FYA) — for qualifying low-emission vehicles and new plant.

If you’ve added assets during the year and they’re not showing in the capital allowances section, go to Fixed assets and verify each asset has a Tax pool assigned.

R&D relief

If your company qualifies for Research & Development tax relief (SME scheme or RDEC), enter the qualifying R&D expenditure under Corporation tax → R&D claim. AccBooks applies the enhanced deduction (or calculates the payable credit for loss-making companies) and updates the computation automatically.

Completing the CT600 form

After reviewing the computation, click Generate CT600. AccBooks maps the computation to the CT600 form boxes and presents a preview. Common boxes:

Box	Description
Box 30	Gross profit or net profit
Box 31	Losses of the period
Box 35	Chargeable gains
Box 37	Total profits
Box 40	Deductions and reliefs
Box 45	Profits chargeable to corporation tax
Box 70	Corporation tax chargeable
Box 85	Marginal relief
Box 90	Corporation tax after marginal relief
Box 475	Tax already paid
Box 480	Tax outstanding

Downloading and filing

1. Once you’re satisfied with the CT600, click Download iXBRL.
2. AccBooks generates the XBRL-tagged document.
3. Log in to HMRC’s Corporation Tax Online service and upload the iXBRL file.
4. Alternatively, pass it to your tax agent — they can file it using their agent credentials.

Direct e-filing from AccBooks to HMRC is on the roadmap.

Paying your corporation tax

Corporation tax is due 9 months and 1 day after your accounting period end — before the CT600 filing deadline. Set up a CHAPS payment or bank transfer to HMRC using:

• Account number: 12001039
• Sort code: 08-32-00
• Reference: your 17-character corporation tax reference (shown on AccBooks’ corporation tax page)