How long to keep w-9 tax form?

You should keep a W-9 tax form for as long as you need it for tax purposes, typically at least until the end of the tax year in which it was issued. If you are using the information to prepare tax returns, retain it for at least three years after the tax return is filed, as the IRS can audit for that period. If the W-9 is related to someone who has not been paid in a while, it's wise to keep it longer in case questions arise. Always check with a tax professional for specific retention guidelines.