Independent Contractor

i am working as independent Contractor as a ERP consultant and I want to know, is it must to send invoices to HO for clients whom I worked for?.

According to Ukba guidelines " If the applicant is a contractor who does not operate either through his/her own company or as an employee, he/she may provide an accountant’s letter confirming a breakdown of his/her gross and net earnings for the period claimed and personal bank statements clearly highlighting all credit payments made to his/her account from employment undertaken during the earnings period claimed".

Is it fine If my accountant can confirm breakdown of gross and net earnings for the period claimed and personal bank statements clearly highlighting all credit payments made to my account from employment undertaken during the earnings period claimed? or I also need to send invoices? but this is not mentioned in HO guidelines