Business · Calculator companion · By K Imports
Preliminary Corporation Tax: practical guide
This guide explains how to use the Count.ie preliminary corporation tax. Compare normal small-company and large-company instalment targets. Follow the inputs, method and worked example below, then compare your own scenario.
Guide written .
Open the Preliminary Corporation Tax calculatorWhat to prepare
- Gather supplier quotes, invoices, time records and the actual scope of the job or business decision.
- Separate revenue from VAT, direct costs from overheads, and profit from the timing of cash receipts.
- Use the same accounting period and currency for related inputs.
Understand the inputs
The calculation method
Small-company lower-of basis, qualifying first-period exemption, or large-company instalments bringing paid preliminary CT to 90% current liability.
Worked example
Illustrative inputs and their result.
Example inputs
- Estimated current CT liability (€)
- 60000
- Prior CT liability annualised to 12 months (€)
- 50000
- This is the first accounting period
- No
- Large-company first instalment actually paid (€)
- 0
Calculated example result
- Preliminary CTTarget
- €50,000.00
- Second Instalment Top Up
- €0.00
How to interpret the result
A profitable estimate can still create a cash shortfall. Read the cost and timing assumptions as well as the headline profit, price or return; the result is a scenario, not a sales forecast.
Keep the scope constant while changing price, volume, supplier cost or time. A lower-sales or higher-cost case helps show whether the decision depends on an optimistic assumption.
Common mistakes to avoid
- Do not confuse markup on cost with margin on selling price.
- Include work that is easy to miss, such as travel, setup, rework and administration, where the model supports it.
- Do not treat tax collected or an unpaid invoice as freely available cash.
Assumptions and sources
Rates/conditions reviewed against the linked official sources on 5 October 2026. Confirm the stated scope before relying on the result.
Rules checked . This date comes from the tool’s review notes and applies only to its documented scope, not to every selectable scenario.
Sources and further information
If your case falls outside this scope, use a more suitable calculator or contact us about an unclear method.