Form 1040 - federal income tax return.
Include all schedules and make sure the return is signed & dated (if self employeed).

Your 2 most recent paystubs.

3 months Bank statements, with all pages for all accounts (checking, savings, money market, 401k, etc).

A copy of your most recent mortgage statement (if refinancing).

A copy of the purchase contract (if applicable).

IF SELF-EMPLOYED:
Year-to-date Profit and Loss (P&L) Statement that is less than 60 days old, and a current signed Balance Sheet.

IF YOU'RE PART OF A CORPORATION OR PARTNERSHIP:
Last year's corporate/partnership tax return, including form K-1. Also, year-to-date Profit and Loss (P&L) Statement (less than 60 days old), and a current signed Balance Sheet.

If you receive a Social Security pension or annuity:
Copy of the benefits statement (Form SSA, etc.) and copy of recent benefit check.

If you own other real estate:
Copies of property tax and insurance bills; Lease/rental agreement (if applicable).

If you receive alimony or child support:
Copy of the divorce decree and evidence of receipt of income for 12 months (e.g., canceled checks, deposit slips or bank statements).

If you pay alimony or child support:
Copy of the divorce decree.

If you currently pay rent:
Copies of rental payments for the last 12 months (may include canceled checks, bank statements, money orders, etc.) and the name and address of your landlord for the same time period.

If you have declared bankruptcy within the last seven years:
Copy of your bankruptcy discharge, a copy of the petition (including schedules A & B) and an explanation of the circumstances.