You report the total amount of foreign tax paid to all foreign entities in the tax year. Period. End of Story.
credit back the excess tax (say $45)next year
Assuming "next year" is 2018, then that $45 dollars is foreign income paid to you in 2018.
Taxes are claimed in the year they are actually paid, regardless of who the tax is paid to or why. (one exception covered below.)
Income is claimed in the year it is physically paid, regardless of who paid it, why they paid, or in what year you actually may have earned that income.
So say your 2015 tax return is audited by the taxing authority and in that audit it's discovered you overpaid your 2015 taxes by $500. They refund you that $500 in 2018. Then it's reportable income on your 2018 return.
Now just like U.S. Taxes, if you file a 2017 foreign tax return for 2017, but you file it in 2018 and you owe 2017 taxes that you pay with that 2017 return when you file it in 2018, then the tax is considered to have been paid with 2017 income, since that's the only income being taxed. So don't over complicate that which is 5-year old simple. You'll just screw yourself up and end up owing penalties, fines and back taxes.
