To complete a self assessment outsourcing, you will need to gather all of your relevant financial documents, including any P60s, P11Ds, or bank statements that show your income and any tax that has already been deducted. You will then need to complete the self assessment tax return form, which includes sections for reporting your income, expenses, and any tax reliefs or allowances you are entitled to. Once you have completed the form, you will need to calculate your outsourc self assessment using the information you have provided. This will involve adding up all of your taxable income, deducting any allowable expenses or tax reliefs, and then applying the appropriate tax rates to determine how much tax you owe.