Is there a limit to donation write-offs?

Is there a limit on how much you can donate and write-off on your taxes?

You may deduct a maximum of up to 50% of your adjusted gross income (AGI) (Line 36 on IRS Form 1040) for the tax year the donation was given. However, if you give more than 50%, the excess may be carried forward for up to five years. Be aware that the 50% rule applies to most contributions, but certain contributions may have lower limits. This is just a basic guideline, everybody is different when it comes to their actual finances and tax returns.

I forget the exact amount but does anyone know what dollar amount your required to keep receipts for? I believe something under like 900 or 1100 you aren't required to keep documentation but anything above that and you are.

According to IRS Publication 1771:

A donor is responsible for obtaining a written acknowledgment from a charity for any single contribution of $250 or more before the donor can claim a charitable contribution on his/her federal income tax return.

A charitable organization is required to provide a written disclosure to a donor who receives goods or services.