Certification of Sole Trader Personal Income for 2015/16

I wish to sponsor my partner's fiancee visa application and need to prove that I meet the financial requirement set by the UK immigration authorities i.e. that my personal income in the last tax year was over £18,600. Once I have taken off my business expenses, by my calculations, my personal income is only marginally above the threshold, so it would be extremely beneficial to the visa application to have that personal income level certified by an accountant so the immigration authorities don't seek to go behind it. The transactional volume is fairly small, maybe around 200 items in total and I have already clearly marked these out under various heads on a copy set of bank statements and a covering spreadsheet. I just need a qualified person to go over everything and certify in writing the personal income total.