What are National Insurance contributions?

In practice, in the UK

National Insurance runs alongside income tax rather than as part of it, with its own classes and its own rules about who is liable, which means a change that affects someone’s income tax position does not automatically affect their National Insurance in the same way. Employees and employers both contribute on employment income, with the employer’s contribution a genuine additional cost on top of gross pay rather than a deduction from it, while the self-employed pay under different classes calculated through their own tax return rather than through PAYE. Because entitlement to certain state benefits depends on a contribution record built up over time, gaps in someone’s National Insurance history — a period abroad, self-employment with low profits, a career break — can have consequences for their eventual State Pension that only become visible many years later.

In Odoo

Odoo’s payroll functionality, or a connected payroll system, calculates and posts National Insurance for both employee and employer alongside PAYE in each pay run, and the employer’s contribution needs to land in the accounts as a genuine cost of employment rather than be netted off against the employee’s own deduction. Getting someone’s employment status wrong in the system — treating a worker as self-employed when National Insurance rules would treat them as employed, or the reverse — carries consequences that go well beyond a single payroll run.

Common mistakes

• Assuming a change to income tax automatically carries across to National Insurance treatment.
• Forgetting that the employer’s National Insurance contribution is an additional cost, not a deduction from the employee’s pay.
• Misclassifying a worker’s employment status, which changes which National Insurance rules actually apply.