I participated in the following program on behalf of the organization I work for.

--First, I flew to city X where I taught for a week.
--Then, I had a week off.  During this week, I flew to city Y and
vacationed, then returned to city X.
--From city X, I flew to city Z and taught for a week, then returned
to city X and flew home.

The organization reimburses me for my expenses up to a certain amount
(the travel budget)--a limit I did not reach.  If I do not reach the
limit, they pay me whatever is left in the budget as salary, but I am
taxed on this amount.  One more detail... the organization promises to
reimburse me a per-diem rate of $75 for food.  I requested that the
following items be reimbursed:

1) The roundtrip flight from home to city X.
2) The rountrip flight from city X to city Y.
3) The roundtrip flight from city X to city Z.
4) 21 days of reimbursement for food (21x$75).

The organization denied me reimbursement for item (2) on the grounds
that I was flying to city Y for vacation.  They further denied me 7
days of per diem on the grounds that I was not working during the
second week.

However, I think the tax code permits them to reimburse me for at
least one of these two (either the flight or the food/hotel for the
week).  Had I flown home in between week 1 and week 3, I would have
had an additional flight to reimburse.  In this case, they wouldn't
have paid for food/hotel, but they should pay for the flight. 
Alternately, I could have stayed in city X, but there, they should
reimburse me for food/hotel.  Does this make sense?

Thank you.

Hello kaxixi7,

Thank you for your question.

This hinges on one important factor-- what is your specific company's
policy on business expenses?  You'll have to look at the actual
business travel policy and see what it says on this matter.  The best
way to put expenses in perspective is to look at a collection of other
organizations' policies for personal travel in relation to company
travel.  Some organizations would reimburse you and some would not. If
you would have submitted only the direct business-related expenses in
the first place, you would have had better luck convincing them to
reimburse you for the flight you didn't take.  If you show them
policies from other organizations, that may help to convince them.

State Of Minnesota---
Charities Travel Policy
http://www.ag.state.mn.us/pdf/charities/TravelPolicy.pdf

"Individuals traveling on behalf of ____________ may incorporate personal travel or
business with their Company-related trips; however, Personnel shall
not arrange Company travel
at a time that is less advantageous to ____________ or involving greater expense to
____________ in order to accommodate personal travel plans. Any additional expenses
incurred as a result of personal travel, including but not limited to
extra hotel nights, additional
stopovers, meals or transportation, are the sole responsibility of the
individual and will not be
reimbursed by ____________. Expenses associated with travel of an
individual?s spouse, family
or friends will not be reimbursed by ____________."

"Personnel traveling on behalf of ____________ are reimbursed for the
reasonable and
actual cost of meals (including tips) subject to a maximum per diem
meal allowance of $38 per
day and the terms and conditions established by ____________ relating
to the per diem meal
allowance."

The Minnesota guidelines are a bit outdated; they mention that if a
Saturday night stay would get a less expensive plane ticket, the
person can be reimbursed for an amount for hotel and food up to the
amount that the more expensive plane ticket would be.  Going by that
guideline, you would be justified in asking for reimbursement of the
amount that the plane ticket to and from City X from home would have
cost the organization.

Lehigh University Travel and Business Expense Policy
http://www.lehigh.edu/~inctr/documents/TravelPolicyStmt2005.pdf
Lehigh University has the same policy:

"The University will reimburse travelers for
additional meals and lodging associated with a longer stay if such
costs are less than the airfare
savings resulting from an earlier arrival or later departure."

"If the traveler takes an indirect route or interrupts a direct route
for other than University
business, reimbursement for air fare will be at either the actual
charge or the charge that would
have been incurred by traveling the direct route by the most
economical means, whichever is
less."

"Unallowable Expense:
-Expenses related to vacation or personal days taken before, during or after a
business trip unless they resulted in the reduction of the total cost of the trip"

According to Lehigh policies, you most likely would have been
reimbursed part of the Week 2 trip.

Not all organizations allow what Lehigh does, however.  Harvard has a
similar policy which includes unallowable expenses but they do not
allow reimbursement for any type of personal expenses at all.

Harvard University
University-Wide Expense Policy
http://vpf-web.harvard.edu/documents/pdf/actts_ubep_5_06_02.pdf

"Unallowable Expenses: Expenses related to vacation or personal days taken before,
during or after a business trip"

Drexel University is similar:
http://www.drexel.edu/depts/compt/travexp.html
"When personal travel is combined with business travel, the University
will reimburse expenses associated with the business portion of the
trip only."

Brown University also has this exact policy.
(Google cache)
http://209.85.165.104/search?q=cache:JscMgEQbOxgJ:www.brown.edu/Administration/Controllers_Office/documents/BusinessExpensePolicyHighlights.doc+business+expenses+personal+expenses+irs&hl=en&gl=us&ct=clnk&cd=3&client=firefox-a

My advice:
You could re-submit the expenses and just ask for reimbursement for
the plane ticket from City X to home which you didn't take.  You would
not be justified in attempting to get all the money back from your
vacation to City Y, according to any organization's policy.  Or, you
could just consider it a learning experience and be glad that you had
such a high per-diem rate for food.  Many of these organizations only
allow $25-50 in food expenses for the day and require proof of
anything costing over $25.

Search terms:
business expenses reimbursed company 
business expenses reimbursed personal
business expenses personal expenses irs

If you need any additional clarification, let me know and I'll be glad
to assist you.

--keystroke-ga

Lets say you work at a place that provides you lunch.  They bring in
food every day and u request what you want.  Now lets say you are out
sick or on vacation one day.  Would you submit your employer a bill
for the lunch you got yourself on the day you did not go to work?  I
do not think so.

You may have already sunk yourself by requesting reimbursement for all
four things-- they may already think you're trying to pull one over on
them.

Your last points are valid, with a few caveats:

Is City Y a popular vacation spot from which flights are very
expensive?  For instance, flying from Pittsburgh to Cincinnati would
probably be less expensive than a flight from Pittsburgh to Bermuda
during that week.

Also, going on vacation, you would eat different food than if you were
stuck in a hotel room in a non-vacation spot for a week-- probably
more exotic and expensive food than typical hotel room fare.

So, more than likely, neither of these are the equal of what the
company would have paid if you'd stayed put or flown back.

I wish I had the problem that my week long vacation was only going to
be subsidized by my employer to the point of my marginal income tax
rate, plus whatever was still left in my travel budget.  At my
employer, a government agency, you aren't allowed to take more than
one vacation day in conjunction with a business trip, lest there be
the slightest whiff of the government subsidizing your vacation.

Jealousy aside, it seems like they should reimburse you for the 7 days
of per diem or another roundtrip ticket to X, although I am curious
what roundtrips from home to X and home to Z would have cost compared
to what you did.

$ 75.00/ day for food?????????????

Wow!!! Pretty generous...

Steph53