Answer Wiki. You don’t and you shouldn’t. If you have forgotten your TIN, maybe you can find it in your bank account application, an old tax return, on a 1099 or W-2 that your business issued, or possibly on your state’s secretary of state business registration website. One of the easiest ways to do so is to visit Google and search for relevant keywords or directly go to bir.gov.ph website. However, if you cannot find the TIN retrieval function, then that’s because, as of writing, there’s no such facility available. For U.S.-based individuals: Your TIN is the same as your social security number. For U.S.-based entities (corporations, partnerships, LLCs, etc.): In general, your TIN is usually the entity’s Federal Employer Identification Number (FEIN). In some cases (e.g., LLC, S-corp corporations, partnerships),