In the past I've got round the need for a US zip code at gas stations by pre-paying at the kiosk. Sometimes they require a passport to validate the credit card and it can get a bit annoying if I forget it and have to scramble for other forms of ID.

I'm now trying to buy transport tickets online (for the flyaway bus from LAX to Union Station, from Metrolink) and am being asked for a zip code when paying with a UK credit card. I know I can queue up to buy a ticket at the kiosk when I arrive at Union Station, but it would be nice not to have to do that.

There are numerous discussions online about how to add zeros to the numbers in a UK post code, but I thought I'd contact my credit card companies for advice to see if they have an official policy.

Amex have said that I can change my account address to a USA address while travelling, then back to my UK address when I return home.

Before I do this, has anyone tried it and does it work?

I've tried using my US address with a Saudi credit card on several websites that required a US zip code and it's been mostly successful. You might luck out be able to purchase it by inserting a random zip code. Or try putting in the zip code for wherever you're staying and see if the purchase works.

I have used UK addresses with my Australian cards and Australian addresses with my UK cards (without changing anything with the banks), on websites in those two countries and others. I can only conclude that some merchants don't bother validating addresses.

Entering just the numbers from UK postcodes works in the UK - except when the website does data validation and refuses a numeral-only entry in the postcode field.

In the US, zip codes are often used as the verification method for credit cards (i.e. if you were using a debit card it'd be a pin number.) So getting the zip code correct can make or break the transaction.

Have you tried entering your current billing information for the card and adding zeros to get to a five digit number for a zip code? Or is the card being rejected? If so I'd try and use a US address if possible, the only down side is that any mail you receive from AMEX will go to that new address. Otherwise you shouldn't have a problem.

As an update, I double-checked with Amex and they said the advice I'd been given by their chat representative was totally incorrect and I shouldn't change my account address during my trip.

The person I spoke to said she'd always managed to get by by using her hotel zip code. Starling Bank said I should use 99999. I've read elsewhere (as suggested below) that padding out my home post code with zeroes was the best option. So.... I'll see what works and what doesn't, and will report back. I've postponed buying the flyaway bus tickets for now, as I may not need them. In fact I may not need a zip code until I hire a car and try to fill up with gas.

In the past I've had varied luck, it really depends on the merchant.

As an update, I double-checked with Amex and they said the advice I'd been given by their chat representative was totally incorrect and I shouldn't change my account address during my trip.

The person I spoke to said she'd always managed to get by by using her hotel zip code. Starling Bank said I should use 99999. I've read elsewhere (as suggested below) that padding out my home post code with zeroes was the best option. So.... I'll see what works and what doesn't, and will report back. I've postponed buying the flyaway bus tickets for now, as I may not need them. In fact I may not need a zip code until I hire a car and try to fill up with gas.

In the past I've had varied luck, it really depends on the merchant.

Depending on where/when you're going you very well might be able to use chip and/or contactless at the pump at least once, which so far is mostly skipping ZIP code prompts. Unfortunately that's nowhere near as common as it should be so I wouldn't rely on that.

(Hint: Speedway, Vons/Safeway and Ralphs/Kroger gas stations support at least chip at the pump. Also, Circle K gas stations will ask for ZIP code with contactless/chip for some stupid reason--even inside.)

I have a credit card issued in Abu Dhabi, where we have no zip or postal codes. I'll enter random numbers and have never had the card rejected.