@Arneoker , my answers in Italics:
1, I suppose I need to obtain the statement showing the payment of this bonus and then file an estimated tax payment. How would that work specifically, especially as this wouldn't be reporting more or less regular income but a one-off bonus?
Because this is "pension", you report it as if a 1099-R was received -- use code 7 for normal distribution, -see instructions for 1099-R here -- 2025 Instructions for Forms 1099-R and 5498.
2. Since of course the exchange rate varies all the time which one would I use? Would it be the exchange rate in effect on the date of the payment?
Ideally you should use the exchange rate in effect at the time of each transaction. However, an annual average published by US treasury or any other published source can also suffice. But be consistent i.e. use the same source for all the transaction(s)
3. From my research I thought that I would be able to get some sort of break on the taxes paid in Colombia on this bonus. Would I at least get a deduction if not a credit?
Please see IRC section 901, 904 for whom and what type of foreign taxes are eligible for foreign tax credit. Two items to note here ---(a) the statute uses "citizen" through out as to whom is eligible. However, and in general US citizen for tax purposes is undisguisable from "US person" used in other statutes --US person implying US citizen, GreenCard holders and Resident for Tax Purposes. Thus the position that for foreign credit to be available for taxes paid to a country, that country must provide a substantially similar tax relief to a US person if he/she were a resident of that country; (b) the statute does not clearly stipulate that there must be a double taxation treaty in effect with the other country but the language used between the different sections of 901, it cannot lead to any other interpretation.
Note also that there is no such limitation ( tax treaty in effect requirement ) for deduction of foreign taxes paid as "State And Local Taxes " subject to SALT limitation , if and only if itemized deduction is used.
Is there more I can do for you ?
