You'll get more responses if you post this on the Europe forum.

Travel.State.Gov is a really good website from the Department of State that covers in easy-to-find way anything you might want to know about international travel.

And you did not ask, but some useful info anyway. When you leave airport in Indiana, airline will ask to see your passport. You don't need a passport of leave the US, but the airline wants to make sure you have necessary documents to return. Assuming you are flying on one ticket/one itinerary thru to London, you do nothing regarding Customs/Immigration until you reunite with your luggage in London.

In London you go thru British Customs/Immigration. Other than waiting in line it should be fast and easy. They will ask to see your passport, and perhaps ask where you are staying, how long, purpose of trip, etc.

Borders are not really anything for any EU country - so the next time you will have any similar experience is when you leave London. Once you land in Indiana you will reclaim your luggage and go thru US Customs and Immigration. You will have filled out a form indicating what you bought while abroad. Limits on this (your original question) are on Dept of State website.

The airline doesn't care if you are returning or not. They want to see your passport to verify you'll be allowed entry into the country you're flying to, as it's their responsibility to fly you back if you are denied entry.

As for what you can bring back, there really is no limit. If you want to buy that $1,000,000 piece of jewelry the US Gov't will not prevent you from bringing it home.

The first $800 per US resident is duty free. Anything more that $800 value and you may be asked to pay a duty (import tax). I don't know exact duty amounts, but they are not prohibitive, and should not prevent you from buying something more expensive than $800. If you can afford the $1,000,000 jewelry then you can afford the duty.

There are limits on tabacco and alcohol that you can import duty free. Many people mistakenly think that they are limited to 1-2 bottle of wine, but that's not the case. The duty on wine is somewhere in the order of 30c per bottle. I've brought back 10-12 bottles several times. I declare the wine on my customs form, but every time I've just been waved through customs.

It's not the State Department that covers custom duty enforcement, it's Department of Homeland Security; specifically, Customs and Border Patrol.
More specifically still, you'll want to check out

www.cbp.gov/xp/cgov/travel/vacation/kbyg/paying_duty.xml

Each person is allowed to bring back up to $800 of goods purchased while in Europe without paying any duty fees. For the next $1000, the duty rate is 3%. These limits can be combined for people traveling as a family. Thus, the two of you can purchase and bring back up to $3600 worth of goods while in Europe and pay no more than $60 in fees.

Before you decide to buy something abroad, get some idea of how much it would cost to buy it in the U.S. There are very few items -- almost entirely high end luxury types -- which can not be imported to here and sold at less cost than buying them in Europe.

Just don't bring back a snowgglobe...the TSA will immediately take you for a bad, bad person.

Not what you asked, but may be of help if you buy a lot of stuff in Europe ... you'll have to pay a large VAT (Value Added Tax ... often 15-20%) upon purchase, but in many/most cases if you are leaving the country with the item you can get a refund on the VAT when you are leaving the country. Worth checking on ...

Here's a link describing more about VAT refunds ...

http://www.ricksteves.com/plan/tips/vat.htm

Agree that you should post on the europe board.

And though you have asked abuot customs (presumably on the way back) you haven;t asked about immigration or customes n the way over.

Into the UK you will have to go through both - Immigration can be long lines - but customs you just walk through the green line (assuming you have nothing to declare on the way in). You will also have to go through Immigration when boarding the Eurostar to paris and back to London - be sure to get to the staion in plenty of time for this - you should plan on doing this at least 30 minutes before the train leaves.

Coming back into the US Immigration is usually fairly quick - unless a bunch of planes land at once - for Customs you will have to have your form filled out - and, if asked, be prepared to produce receipts for what you bought. Usually this is routine - but a few people are picked out for a complete search of their luggage. (Famously ome years ago a Bloomingdale family member and friend were caught bringing back large amount of jewelry and designer clothing that they did not declare - and faced really bad press as well as duties and penalties for not declaring.

The $800 allowance is usually plenty now - since almst everything is much cheaper inthe US than in europe.

Thank you all! I will post it in the Europe Forum too. You all have given me so much info! Stuff I didn't even realize I needed to know. Thank you!

IF you are going to claim the VAT refund at the airport allow for a LOT of time to do so. The lines were so long in CDG last year, we gave up waiting and said forgetaboutit, we would have missed our flight.

You will go through US immigration and customs at the first US port of entry.

Sample of US customs form:

http://www.cbp.gov/xp/cgov/travel/vacation/sample_declaration_form.xml

One thing I forgot to mention, simply because it usually isn't an issue for tourists.

If you leave or enter the U.S. with a total of $10,000 or more (or foreign equivalent) of currency or negotiable securities (ie, checks, stocks, or bonds) in your physical possession, you must DECLARE that fact. It is not illegal to carry any amount of money across a U.S. border, but do not "forget" to mention doing so if over $10,000 -- customs agents would take such a violation VERY seriously.

Thank you!

Be sure to leave extra time to cash in your VAT tax receipts at the airport. If the terminal is large, your might have a long walk. YOu can only get a VAT refund on purchases if the store gives you the VAT receipt. Not all shops do this.

On the return flight be sure that you get an Immigration/Customs form on the plane. I take a couple extra and keep with my passport because I sometimes miss the distribution (?bathroom?, ?asleep?).

Keep receipts for everything that you purchase and take home in a special envelope and bring the receipts on the plane. YOu can group multiple items into a category (e.g. clothing) to itemize with the total on the form. YOu will also need your passport number so don't put it in the overhead compartment.

I was told by a Customs official that items purchased in Duty Free shops must also be listed.

Have fun shopping!

You don't have to go into much detail on the US customs form.

Just a basic item, # and dollar value

3 T-shirts, $20
1 bottle perfume, 4 oz, $70