Unsupported Tax Features & Workarounds

TinyTax is designed for straightforward company filings. Some advanced CT600 features are not yet supported as dedicated fields. This guide explains what's not available and how to work around common situations.

What TinyTax Supports

TinyTax handles the most common filing scenarios:

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What's Not Currently Supported

The following CT600 boxes and features do not have dedicated fields in TinyTax:

Chargeable Gains (Capital Gains)

Box	Description	Status
210	Chargeable gains (net gains after losses)	Not supported
215	Gains qualifying for investors' relief	Not supported
220	Gains qualifying for BADR	Not supported
825	Allowable capital losses	Not supported

Typical use case: Companies that sell investments, property, or shares at a profit. Limited companies pay corporation tax on chargeable gains, not CGT.

Writing Down Allowances (WDA)

Box	Description	Status
Various	WDA at 18% main pool rate	Not as dedicated field
Various	WDA at 6% special rate pool	Not as dedicated field

Typical use case: Companies with capital expenditure exceeding the AIA limit, or assets that don't qualify for AIA (e.g., cars with CO2 emissions).

Investment Company Features

Box	Description	Status
245	Management expenses	Not supported
620	Franked Investment Income (FII)	Not supported
625	Number of 51% group companies	Not supported

Typical use case: Holding companies receiving dividends from subsidiaries.

Other Advanced Features

Feature	Status
R&D tax credits	Not supported
Group relief	Not supported
Patent box	Not supported
Northern Ireland trading profits	Not supported

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Workarounds Using Existing Fields

For many situations, you can achieve the correct tax payable using TinyTax's existing fields. The key is the Other adjustments field and Annual Investment Allowance.

How to Access These Fields

In the Tax Computation - Current Year section header, you'll see a Show all link on the right side. Click it to reveal all available adjustment fields:

Show all

After clicking, it changes to "Hide empty". This reveals several fields including:

Field	Box	Use For
Other adjustments (add if positive, deduct if negative)	—	Any adjustments not covered by other fields
Less: Annual Investment Allowance	735	100% first-year allowances on qualifying equipment
Add back: Depreciation	—	Automatically populated from P&L
Add back: Disallowable expenses	—	Client entertaining, fines, penalties

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Working Around Specific Limitations

Writing Down Allowances (WDA)

If your WDA qualifies for 100% relief (e.g., electric vehicles, zero-emission goods vehicles):

Use the Annual Investment Allowance field. First-year allowances for zero-emission vehicles are effectively the same as AIA - 100% relief in year one.

If your WDA is partial (e.g., 18% main pool rate, 6% special rate):

1. Calculate your WDA amount manually (e.g., £10,000 asset × 18% = £1,800)
2. Enter as a negative number in Other adjustments:

The negative value reduces your taxable profit, giving you the tax relief.

Chargeable Gains

For companies with chargeable gains (e.g., profit on selling investments or property):

Very simple gains (where the gain is straightforward to calculate):

1. Calculate your chargeable gain manually:

- Disposal proceeds minus original cost minus allowable costs - Apply any reliefs (indexation, etc.)

1. You have two options:

Option A - Include in trading profit: Add the gain to your profit figure before entering in TinyTax. This works if you're comfortable reporting the gain within your trading profits.

Option B - Use Other adjustments: Enter your normal trading profit, then add the chargeable gain as a positive adjustment:

Both approaches result in the same tax payable, but the CT600 won't show the dedicated chargeable gains boxes.

Investment Company Income

For holding companies with dividend income or management expenses:

Dividend income (Franked Investment Income): UK dividends received from other companies are exempt from corporation tax. You don't need to report them in your taxable profit - simply exclude them from your figures.

Management expenses: Enter as a negative number in Other adjustments:

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When to Use Specialist Software

TinyTax may not be suitable if your company has:

• Significant chargeable gains - selling investments, property, or shares for substantial profit
• Complex capital allowances - multiple pools, balancing charges, or short-life assets
• Investment company structures - pure holding companies with management expenses
• R&D activities - claiming R&D tax credits
• Group structures - group relief claims between companies
• Northern Ireland trading - separate NI profits calculation

In these cases, consider:

• Full CT600 software (TaxCalc, Taxfiler, etc.)
• Using an accountant who can file on your behalf
• HMRC's own CT600 filing service (basic but comprehensive)

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Roadmap

We're working on expanding TinyTax to support more scenarios. Planned additions include:

• Investment company features (management expenses, FII)
• Chargeable gains reporting
• Additional capital allowance options

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Still Have Questions?

If you're unsure whether TinyTax can handle your situation, contact us with details about your company and we'll advise.

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Last updated: January 2026