Known limitations
Honest boundaries of the currently reviewed Sterling corpus.
The wiki is deliberately incomplete. It does not yet establish the start date of the £85,000 VAT period or decide place-of-supply, transfer-of-going-concern, land, mixed-supply, or capital-asset cases.
The Corporation Tax calculator is limited to ordinary UK-resident companies with explicit taxable total profits, qualifying non-excluded exempt distributions, associated-company count, close investment-holding-company status and ring-fence status. It does not decide those legal facts, calculate ring-fence or mixed profits, model changes in associated companies within a period, or produce a submission. CT600 serialization and rounding remain a separate unimplemented and unverified boundary; displayed results are not filing values.
The expense-timing calculator handles ordinary GBP service costs using an explicitly evidenced straight-line daily or whole-month allocation, or an independently known accrued amount. It does not decide whether that policy reflects consumption, reconstruct opening balances, determine VAT or Corporation Tax, or replace specialist lease, inventory, payroll, grant, financing, foreign-currency, impairment, provision, or contingent-liability treatment. Every journal is a draft and is never posted automatically.
The owner-director branch does not yet decide realised-profit classification, public-company and investment-company restrictions, distribution-in-kind valuation, share-class entitlement, benefits-code calculations, anti-avoidance around repayments, or the borrower's tax on release and write-off. A company-specific dividend answer still needs relevant accounts, the proposed amount, and liquidity facts.
Sterling refuses to infer an unreviewed rate or missing customer fact.
Return to coverage · See open research questions
Companies House boundary
This branch does not reconstruct pre-6 April 2008 Companies Act 1985 accounts deadlines or pre-30 June 2016 annual returns. Exact historic temporary outcomes can depend on savings and the original deadline. For a company-specific answer Sterling therefore needs the registered due date and a fresh register observation; it does not infer an extension or file anything.
Capital-allowance boundary
The current calculation supports AIA, main and special pools, writing-down allowances, small-pool relief and ordinary disposal values. Sterling full expensing and first-year allowances are not calculated, nor are structures and buildings allowance, short-life or single-asset pools, long-life assets, ring-fence cases, successions or hire purchase. Sterling never turns a computed maximum into a filed claim and never invents opening pools, asset eligibility, group allocation, disposals or taxable profit.
Class 1 National Insurance boundary
The calculated path requires an explicitly confirmed category A, non-director employee, payment date, weekly or monthly earnings period and gross National Insurance earnings. It does not cover other category letters, directors' annual or alternative method, deferment, aggregation, irregular or multiple-week pay, payments after leaving, Class 1A or 1B, Employment Allowance, PAYE Income Tax, pensions, student loans, statutory payments, net pay, RTI, posting or payment. Sterling never substitutes a current rate for an uncovered period.
Personal Income Tax boundary
The simple non-savings calculation does not cover savings income, dividends, PAYE, tax already deducted, property-income rates from 2027–28, specially rated income, reliefs, rate-band extensions or allowance adjustments. The separate bounded savings calculation covers ordinary non-savings plus savings income only. Both require the taxpayer regime, adjusted net income and supported income to be explicitly established. Neither determines residence, Scottish or Welsh taxpayer status, a complete Self Assessment liability, payments on account or a filing value.
Savings Income Tax boundary
The bounded calculation accepts only ordinary non-savings plus statutory savings income, the standard Personal Allowance and an established taxpayer regime. It refuses dividends, chargeable gains, foreign income, trusts, estates, remittance-basis cases, other specially treated income, reliefs, Gift Aid, pension band extensions and tax deducted at source. It is not PAYE, a complete Self Assessment result, a payment amount or a filing value. From 2027–28, enacted savings and property changes remain future knowledge until a complete annual calculation set is reviewed.