Do I need to upload both payslips and bank statements?

If you're employed, you should try to upload both payslips and bank statements. If you've recently started a new job or are due to start in the near future, you won't have received any payslips yet and you may not have been paid your monthly salary yet, so you'll need to upload a full employment contract to your application and make sure to enter valid employment referee details so that Let Alliance can obtain a reference.