INDIVIDUAL
1040-ES – Estimated Tax for Individuals (IRS)
http://www.irs.gov/pub/irs-pdf/f1040es.pdf
“Where’s my refund?” Online Status Checker
https://sa2.www4.irs.gov/irfof/lang/en/irfofgetstatus.jsp
BUSINESS/CORPORATE
W-4 – Employee’s Withholding Allowance Certificate
http://www.irs.gov/pub/irs-pdf/fw4.pdf
W-9 – Request for Taxpayer Identification Number and Certification
http://www.irs.gov/pub/irs-pdf/fw9.pdf
Application for Employer Identification Number (Online portal – no form needed!)
https://sa2.www4.irs.gov/modiein/individual/index.jsp
Application for Employer Identification Number (form)
http://www.irs.gov/pub/irs-pdf/fss4.pdf
1120-W – Estimated Tax for Corporations (IRS)
http://www.irs.gov/pub/irs-pdf/f1120w.pdf
990-W – Estimated Tax on Unrelated Business Taxable Income for Tax-Exempt Organizations
http://www.irs.gov/pub/irs-pdf/f990w.pdf
I-9 – Employment Eligibility Verification
http://www.uscis.gov/i-9
Don’t see the form you want? The IRS maintains a great database of both current and past tax forms. Access them here: http://www.irs.gov/Forms-&-Pubs