If your actual accounting information is truly and permanently gone, that's both a problem and an opportunity: you can't get it anymore, but neither can the tax authorities.<p>So, the next best thing you can do, is submit a best-faith declaration. I assume you still know how much you spent on source materials (in case you did physical sales), or approximately how many units at which price points you sold (for digital sales).<p>You then construct a Profit-and-Loss statement based on these best-faith assumptions, and go with that. It's quite unlikely the tax authorities will challenge you on this, <i>unless</i> Amazon happens to have communicated sales (and/or sales tax) amounts to them already.<p>If that is the case, and you best-faith declaration varies significantly from those reported amounts, you may face audits and/or fines. Prior to doing your tax filing, you <i>may</i> be able to obtain any pre-reported amounts from Amazon and/or the tax authorities: if you're going to spend any money on "fighting" this, I would invest it in a tax lawyer licensed in your jurisdiction to send the required requests.<p>However, also consider the monetary upside/downside of doing such. In many jurisdictions, fines for tax under-reporting are typically capped at 100% of the final tax amount. So, if you would owe, say US$ 5K according to your own calculations, and that actually turns out to be 10K, the maximum total damage (tax plus fine) you would realistically face would be around 20K. Then, see how much lawyering and anguish you would get for the difference...