I am assuming that you lost your tax file for 2012 that you need to prepare your taxes. First thing would be to write a list of everything that you had in the file. If you are unsure you can look at previous tax returns to see what you had reported the previous year to get an idea of what you would have this year. Since your file was lost in a flood I would almost assume that your previous tax returns might be lost as well. You should be able to contact the CPA who prepared your previous returns to get a copy. If you self prepared or the CPA who prepared your return is no longer in business you can request a transcript from the IRS for the tax years you need. Once you know what you are missing I would try to contact the company or agency that sent you the original documents to see if you can get duplicate copy.

If you are unable to get a copy of all the documents that you need you are allowed to estimate on your tax return. It is recommended that you disclose that the records were lost if it was due to a flood or other natural disaster. If they were not lost due to these types of incidents it is not recommended that you disclose this information. When estimating on your tax return you are not allowed report numbers that are more accurate than they are. Simply put, if you made a donation to a church and you think you donated $110.67 you should report $100.00 on your tax return and not $110.67.

I would try to get duplicate copies first and use estimation for only the items that you are unable to secure.

Philip L. Yasenak

Based on our experience in Australia, you can inform the authority such as Government (In Australia we have ASIC). You will be able to recreate your accounts and files (not 100% accurate, but reasonably well based on the information you can gather) from your bank statements, your clients’ bank statements to support your claims as well as electronic tax return files held by the Government. Bank, the tax authority will be able to provide you copies of your statements and tax returns upon your request. In situations like this, the CPA and CA accountants will have organised a committee to help out businesses on volunteer basis.

We had Bush fire incidence in Australia, where CPA Australia's members had organised volunteer work for Bush fire victims who have lost all their documents in Bush fire. The Australian Taxation Office also put a plan in place to give extension of time to Bushfire victims and businesses that were affected. Hope this example gives information you are looking for.

All the best!

Assuming this is a return which has already been filed with the IRS, you can get a copy of your transcripts from the IRS. If it has not been filed, (2012) the IRS will have copies of your tax documents sometime after March or April of 2013. If necessary, file an extension. Make sure you file it before April 15, 2013. This will give you an additional six months to file your return.
Phillip Yesanak's answer to your question is very thorough.