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Filing Your First CT600

Step-by-step guide to filing your first CT600 corporation tax return with TinyTax. Covers company type selection, P&L entry, balance sheet, and HMRC submission.

Prior Year Filed Elsewhere

Mark previous CT600 periods as filed elsewhere if you used an accountant or other software. Unblock current filings without refiling old periods.

Capital Allowances & Annual Investment Allowance

Claim tax relief on business equipment with Annual Investment Allowance (AIA). Learn what qualifies, limits, and how to enter capital allowances in TinyTax.

Losses: Brought Forward & Carried Forward

Use previous year losses to reduce corporation tax. Learn how brought forward losses work, where to enter them, and how they offset profits.

CICs and Companies Limited by Guarantee

File CT600 for Community Interest Companies (CICs) and Companies Limited by Guarantee (CLGs). Learn what TinyTax supports for these special company types.

Dormant Company Filing

File your dormant company CT600 for free with TinyTax. Learn what counts as dormant, which fields to complete, and the difference between HMRC and Companies House dormancy.

Extended Accounting Periods

Why accounting periods over 12 months require two CT600 returns, and how TinyTax automatically splits your figures and generates both submissions.

Filing an Amended CT600

How to file an amended CT600 when HMRC already has your return. Fix errors in figures, correct information, or respond to HMRC queries.

Understanding Your Tax Calculation

Understand how corporation tax is calculated from your accounting profit. Explains key CT600 boxes, disallowable expenses, capital allowances, and tax rates.

Getting Started: Dashboard & Navigation

Learn how to navigate your TinyTax dashboard. Understand status icons, start filings, return to drafts, and use the company details drawer.

Saving Your Work & Returning to Drafts

TinyTax saves automatically - no save button needed. Learn how your data is preserved and how to return to unfinished filings.

Importing from Trial Balance

Import your trial balance from Xero, QuickBooks, Sage, FreeAgent and more. Skip manual entry by uploading CSV, Excel, or pasting data directly.

Troubleshooting Common Errors

Fix common TinyTax errors including HMRC Error 3001, authentication failures, invalid UTR, and Companies House auth code issues.

Companies House Auth Codes

Find your Companies House Authentication Code for filing accounts. Learn where to locate it, how to request a new one, and fix common auth code errors.