SH.123 Hussain

Hi I offer legal services as an agent for law firms and once this service has concluded I invoice the firm for the cost of legal services, mileage and parking fees. I am registered as self employed so when completing my tax returns should I include my income as the total of what I have received including my charges for legal services, mileage and parking or should mileage and parking be excluded? If parking and mileage should be included as my income, should I then also claim mileage and parking as an expense? My second question is that should I only be declaring my income for invoices I have been paid for within the financial year or should it also be for invoices I have sent in the financial year but have been paid in the following financial year. Thanks