In the offer form, you're asked to provide your total gross annual income amount. As such, you will need to input your combined income from all jobs or income sources you have. For example, if you're employed and earn £25,000 but you're also self-employed and earn £3,000 a year, you'll need to select 'Employed' as your main income source and enter £28,000 as your total annual income amount. If you have more than one job, you'll need to select the employment type that is stated in your employment contract for the job that provides your main source of income.
If your offer is approved, you'll be asked to provide specific details for each employment type and income source, so you'll be able to provide further information later on in the process. If you're not sure what your total gross annual income amount is, please provide an honest estimate.