I'm trying to transfer money that was held in a US bank (but is now held in BarclaysX) to a UK bank account. Would I have to pay tax to the IRS?

[JadeH94]

This is money that was recovered from a scam and the US bank account was not my own.

[Anonymous]

transferring money from a bank a/c in the US to a bank a/c in the UK is in and of itself is not a taxable event for US purposes. most important is the source of that money and whether you as a US citizen paid US taxes on it if it was income

[JadeH94]

I am not a US citizen. I was scammed out of my life savings but someone involved in the scam took pity and was able to get my money back for me, I am now in the process of attempting to transfer it into my account but wanted to check if I was liable to some kind of tax in the US as it had been held in a US bank account. 

[Opus 17]

No.  Transferring money between two accounts that you own is not a taxable event, regardless of whether you are a "US person" for income tax purposes.

If you are a US person (means a citizen, green card holder, or a resident alien who passes the substantial presence test) then you need to file a report of foreign bank accounts (FBAR) if you have a foreign account worth more than $10,000 in US funds.  This is a report only, no tax is owed. 

If the amount transferred is more than $10,000, the bank files a report, but you don't have to do anything.  If the transfer is more than $10,000, don't split it into smaller transfers of less than $10,000 because this looks suspicious and can sometimes constitute a crime called "structuring" even if the money and the transfers are perfectly legal otherwise.  

In some cases, a gift by a non-US person of physical property located inside the US (like real estate, or other tangible assets) is subject to a gift tax, but this rule never applies to money assets.