If your company fails to pay the old-age insurance, you need to pay it back. You can declare personal income tax through the following steps: prepare all the required information, including your identity certificate, old-age insurance payment voucher and other related documents. Open the website of China State Taxation Administration of The People's Republic of China and log in to your personal tax account. Select the "Declaration" option, and then select "Personal Income Tax". Fill in relevant information according to the prompts, including your personal information, pension insurance payment and other related information. Upload your old-age insurance payment voucher and other related documents. Complete the tax return according to the prompt. If the unit fails to pay the endowment insurance, you need to bear the responsibility of paying it back. So you need to calculate the amount you need to pay back, and then hand it over to the tax authorities when you declare personal income tax.