Many pension schemes calculate your contributions on a basis of ‘qualifying earnings’. This means that they look at your earnings between two thresholds. Currently, these are £6,240 and £50,270.
E.g. if you earn £37,000, your pension contributions would only be calculated based on £30,760 (£37,000-£6,240). If you earn £60,000, your pension contributions would only be calculated based on £44,030 (£50,270-6,240).