UK/USA tax. How to annually claim tax credit at IRS for UK tax paid.

[Uncertain1]

Can anyone please describe how, if filing both UK and USA (federal only) tax returns, one handles the time offset of the filing periods/deadlines and the implications that this time offset has on annually administering and claiming the credit at IRS for tax paid to UK HMRC.

For example, if a UK individual has only some small UK based incomes (but an obligation to also file federal US 1040) then under the taxation treaty UK HMRC will expect first shot at taxing this UK income. If the USA tax payable on this same income works out as slightly less than the UK obligation, then assuming IRS allows (on the 1040) a tax credit for the UK tax paid to HMRC, then in theory there should be no tax payable to USA.

A complication is that USA tax return is usually filed BEFORE the UK tax return. For USA, 15 October (even with extension) whereas UK deadline 31 January following year.

So how does one calculate and show the “UK tax paid” when completing the 1040. It seems there might be various possible ways to do this:-

1) Do a calculation of what UK tax is going to be and show this as UK tax paid, though it might not yet have actually been paid because UK return has not yet been submitted. Actually the 1 January to 5 April portion would have been paid to HMRC (on last years UK return), but not yet for the other 9 months of 6 April to 31 Dec.

2) File the UK return early, so that this later 9 month portion can also be stated as already paid to HMRC.

3) Pay the tax twice, once to IRS (unnecessarily) and once to UK HMRC (necessary) and then claim back a credit from IRS the following year. Getting a refund back from IRS has other uncertainties too, from my past experience.

Which procedure is normally used, or is there some other?

Thank you in advance for your replies


CONTEXT
British, living in UK, But with obligation for US tax and to file a 1040, due to a past green card.
Retired. No wages/salary income. No US income. No US property. No US financial interests. No time now spent in USA.
Small UK income comprising:-
UK private pension, £14,000/yr. (no state pension incomes)
UK savings interest £20,000/yr
renting out of a UK property. £20,000/yr

[DavidTreitel]

The UK rental activity is reported on Schedule E plus Form 8858 and Form 1116. All 3 forms are required each year. To ensure there are adequate credits to claim
in the US, most people accelerate payments to HMRC.

[Uncertain1]

Thank you David. That all makes sense. Form 1116 looks straightforward enough, to list the different categories of income and claim tax credits for each for the UK taxes paid and even carry forward any leftover credits. All best.