How SlipSense builds its readout

SlipSense uses visible arithmetic, cautious payroll heuristics, and public UK guidance on payslip contents, tax-code patterns, and National Insurance categories. It is meant to reduce confusion, not to overclaim certainty.

Core logic

• It adds the visible deduction lines and checks whether they broadly reconcile with gross pay and net pay.
• It converts large deduction shares into plain-language warnings and payroll questions.
• It recognises common UK tax-code families such as 1257L, BR, D0, D1, 0T, K codes, and emergency suffixes like W1, M1, or X.
• It explains common NI categories with conservative wording rather than pretending every category means the same thing for every worker.
• If hours are entered, it adds an hourly gross/net view to make variable-pay months easier to compare.

Reference sources used for the build

• GOV.UK payslip rights guidance: employers must provide payslips on or before payday and show gross pay, net pay, variable deductions, and hours where pay varies with time worked.
• Acas payslip guidance: workers and employees should receive itemised pay statements and can raise errors informally first, then formally if needed.
• GOV.UK tax-rate and National Insurance category guidance: used only as context for cautious pattern explanations, not for exact payroll recalculation.

Why the language is cautious

Payroll can change because of cumulative tax, prior-period adjustments, salary sacrifice, attachment orders, student loan plans, bonuses, minimum-wage catch-ups, or employer-specific earning codes. SlipSense therefore frames output as “worth checking” rather than “wrong”.