Unless you fail to pay your taxes, or give someone grounds to sue you and win, getting a court judgment against you, or owe child suport or alimony, or got the money through criminal means (e.g. drug sales), your money cannot simply be "seized." There needs to be some legal reason--which means some wrongdoing you did--which lets a government agency (IRS) or the courts take your money. Simply not having "proof" of how you got the money by itself does *not* give anyone grounds to take it: rather, there must be proof of the wrondoing, etc. which would let the government or courts seize or take the money. So unless you are aware of some wrongdoing you have done, there is no reason to fear this.