I donate $100 to a different charity each week, but most do not issue
a receipt because the donation is under $250. Does it look bad to
deduct $5200 from my taxes without the receipts to back it up? Can I
ask for a receipt from the charities? Should I change to donating $250
every 2 1/2 weeks?

Hi Darrenlu,

According to the IRS (I'm assuming you're an American, please advise
if this is incorrect), you should be getting receipts from every
charity to whom you donate:

"You must keep records reflecting the amount of cash and noncash
contributions you make during the year. The types of records you must
keep depend on the amount of your contributions and whether they are
cash or property.

Note: A qualified organization must give you a written statement if it
receives a payment of over $75 from you, and your payment is partly a
contribution and partly a payment for goods or services. Keep the
written statement for your records."
http://www.irs.gov/individuals/article/0,,id=132944,00.html

And continuing...
"For a cash contribution, the type of records you are required to keep
depends on whether the contribution is:

Less than $250, or  
$250 or more 
In figuring whether your contribution is $250 or more, do not combine
separate contributions. Each payment is a separate contribution."
http://www.irs.gov/individuals/article/0,,id=132945,00.html

And further...
"For each cash contribution under $250, you must keep one of the following:

A cancelled check or a legible and readable account statement that
contains the amount of the contribution, the date posted (or
transaction date if the contribution was charged to a credit card),
and to whom paid.


A receipt (or a letter or other written communication) from the
qualified organization that contains the name of the organization, the
date of the contribution, and the amount of the contribution.

Other reliable written records that provide the name of the qualified
organization, the date, and amount of the contribution. Your records
are generally considered reliable if they were made at or near the
time of the contribution and were maintained by you. If, in the case
of small donations, you have a button, emblem, or other token
regularly given to taxpayers making small cash contributions, these
items may satisfy your recordkeeping requirements for the small
donations.
For additional information on recordkeeping requirements, refer to
Publication 526, Charitable Contributions. Publication 526
[http://www.irs.gov/pub/irs-pdf/p526.pdf] is available for download or
you may request a copy by calling 1-800-829-3676."
http://www.irs.gov/individuals/article/0,,id=132951,00.html

If you have not got some kind of records to back up your charitable
contributions, then you aren't allowed to take them, per "You are not
allowed to deduct your charitable contributions because you did not
satisfy the acknowledgement and recordkeeping requirements."
(http://www.irs.gov/individuals/article/0,,id=132935,00.html)

These pages are successive steps in the Charitable Contributions Tax
Trail from the US IRS
(http://www.irs.gov/individuals/article/0,,id=132931,00.html).  I
found this by going to the IRS and selecting information for
individuals, then a search for "receipts and deductions".

Please let me know if I can clarify this answer further!

Yours, Librariankt

Wow, thanks for the great answer. That clears things up a bunch.

What you are doing - $100 per week - is perfectly legitimate without a
receipt. However, as you note, it may look suspicious. Deductions for
charity that are significantly more than a typical person in your
income range can be a trigger for an audit as I've read.  To protect
yourself, I would recommend giving the donation by check and keeping
copies of the cancelled checks. That should be sufficient to answer
any questions from the IRS.

I would agree with the above advice. But you can also request a
receipt from the Organizations you have donated to also. Any
organization that won't send a receipt does not deserve a donation.

-non profit climber-

May the Lord lead you, and you be wise enough to follow.

Always ask for a receipt - if they are unwilling to provide one then
they may not be using the donations as promised, if all else fails
write a check, purchase a money order, or get a certified check for
the amount - that way you are automatically provided with a receipt. 
A final option is to set up automatic debit contribution, your bank
statement will be proof enough for the contribution.