For tax returns, pay attention to the real electronic signature string of tax returns, and the last number is =; For the tax deduction certificate, pay attention to whether the date on the surface matches the number in the upper right corner and the location of the tax deduction triangle. Of course, the most important thing is to check the customer's tax control information on the spot, such as whether the current invoice is consistent with the tax return, and whether the number of declarations on the tax return is consistent with that on the tax bill. Note that tax bills are printed electronically, and it is impossible to distinguish between true and false, but the tax return can be printed on the spot to verify the authenticity of the tax bill. In addition, the authenticity of the tax bill can also be assisted by the real bank statement.