ETA: I am not an accountant and the information contained in this post is not to be construed as financial advice. This post consists solely of personal opinions and links referencing information used to form those opinions.for US citizens:
from
http://www.law.cornell.edu/uscode/text/26/985:
(a) In general
Unless otherwise provided in regulations, all determinations under this subtitle shall be made in the taxpayer’s functional currency.
(b) Functional currency
(1) In general
For purposes of this subtitle, the term “functional currency” means—
(A) except as provided in subparagraph (B), the dollar, or
(B) in the case of a qualified business unit, the currency of the economic environment in which a significant part of such unit’s activities are conducted and which is used by such unit in keeping its books and records.
Translation: if you aren't a business, you not only do your taxes in dollars, like all US citizens, but you also keep track of everything in dollars, presumably even in foreign countries, making the above argument moot if not wrong.
from
http://www.law.cornell.edu/uscode/text/26/988:
(a) General rule
Notwithstanding any other provision of this chapter—
(1) Treatment as ordinary income or loss
(A) In general
Except as otherwise provided in this section, any foreign currency gain or loss attributable to a section 988 transaction shall be computed separately and treated as ordinary income or loss (as the case may be).
Translation: ordinary income or loss means you pay your full marginal tax rate (no long term gains or losses to benefit from). Also, notice "any ... transaction shall be computed separately".
(3) Source
(A) In general
Except as otherwise provided in regulations, in the case of any amount treated as ordinary income or loss under paragraph (1) (without regard to paragraph (1)(B)), the source of such amount shall be determined by reference to the residence of the taxpayer or the qualified business unit of the taxpayer on whose books the asset, liability, or item of income or expense is properly reflected.
(B) Residence
For purposes of this subpart—
(i) In general The residence of any person shall be—
(I) in the case of an individual, the country in which such individual’s tax home (as defined in section 911 (d)(3)) is located
Translation, your bitcoin were earned/bought at home (as was the foreign currency bought when traveling)
(b) Foreign currency gain or loss
For purposes of this section—
(1) Foreign currency gain
The term “foreign currency gain” means any gain from a section 988 transaction to the extent such gain does not exceed gain realized by reason of changes in exchange rates on or after the booking date and before the payment date.
(2) Foreign currency loss
The term “foreign currency loss” means any loss from a section 988 transaction to the extent such loss does not exceed the loss realized by reason of changes in exchange rates on or after the booking date and before the payment date.
Translation: all gains and losses an foreign currency are based on the exchange rate (given this, gains/losses above and beyond the exchange rate may be treated differently for tax purposes, but let's assume exchanges are done at market rate, and there are no other gains and losses, because the exchange rate is certainly going to account for the majority of the gains and losses)
(c) Other definitions
For purposes of this section—
(1) Section 988 transaction
(A) In general
The term “section 988 transaction” means any transaction described in subparagraph (B) if the amount which the taxpayer is entitled to receive (or is required to pay) by reason of such transaction—
(i) is denominated in terms of a nonfunctional currency, or
(ii) is determined by reference to the value of 1 or more nonfunctional currencies.
(B) Description of transactions
For purposes of subparagraph (A), the following transactions are described in this subparagraph:
(i) The acquisition of a debt instrument or becoming the obligor under a debt instrument.
(ii) Accruing (or otherwise taking into account) for purposes of this subtitle any item of expense or gross income or receipts which is to be paid or received after the date on which so accrued or taken into account.
(iii) Entering into or acquiring any forward contract, futures contract, option, or similar financial instrument.
The Secretary may prescribe regulations excluding from the application of clause (ii) any class of items the taking into account of which is not necessary to carry out the purposes of this section by reason of the small amounts or short periods involved, or otherwise.
(C) Special rules for disposition of nonfunctional currency
(i) In general In the case of any disposition of any nonfunctional currency—
(I) such disposition shall be treated as a section 988 transaction, and
(II) any gain or loss from such transaction shall be treated as foreign currency gain or loss (as the case may be).
(ii) Nonfunctional currency For purposes of this section, the term “nonfunctional currency” includes coin or currency, and nonfunctional currency denominated demand or time deposits or similar instruments issued by a bank or other financial institution.
Translation: when you buy, sell, borrow, loan, or contract anything, it is a foreign currency transaction if foreign currency or nonfunctional currency is involved.
(e) Application to individuals
(1) In general
The preceding provisions of this section shall not apply to any section 988 transaction entered into by an individual which is a personal transaction.
(2) Exclusion for certain personal transactions
If—
(A) nonfunctional currency is disposed of by an individual in any transaction, and
(B) such transaction is a personal transaction,
no gain shall be recognized for purposes of this subtitle by reason of changes in exchange rates after such currency was acquired by such individual and before such disposition. The preceding sentence shall not apply if the gain which would otherwise be recognized on the transaction exceeds $200.
(3) Personal transactions
For purposes of this subsection, the term “personal transaction” means any transaction entered into by an individual
Translation: because you're an individual, you don't have to keep track of transaction where you gain less than $200, but you also don't get to claim losses, ever (-$1000 does not exceed +$200).
As I was saying, you have to keep track of your cost basis because the code says in my first quote and also in order to know whether or not a gain exceeds $200. So your record keeping requirements do not change based on treating BTC as currency (foreign or nonfunctional). Moreover, as I already mentioned, treating it as foreign currency could effect FATCA requirements. Finally, if you bought one BTC for $30 and bought a $500 leather jacket for one BTC over one year later with no other capital losses to report, using 2014 tax brackets, and based on your income assuming you are single, you would owe the following additional taxes:
Adjusted Gross Income: $9075 or less
BTC as Currency (10%): $47
BTC as Asset (0%): $0
Adjusted Gross Income: $9076-$36,900
BTC as Currency (15%): $70.5
BTC as Asset (0%): $0
Adjusted Gross Income: $36,901-$89,350
BTC as Currency (25%): $117.5
BTC as Asset (15%): $70.5
Adjusted Gross Income: $89,351-$186,350
BTC as Currency (28%): $131.6
BTC as Asset (15%): $70.5
Adjusted Gross Income: $186,351-$405,100
BTC as Currency (33%): $155.1
BTC as Asset (15%): $70.5
Adjusted Gross Income: $405,101-$406,750
BTC as Currency (35%): $164.5
BTC as Asset (15%): $70.5
Adjusted Gross Income: $406,751+
BTC as Currency (39.6%): $186.12
BTC as Asset(20%): $94
For the record, this is a gain of $470, and the minimum income amounts on all of those examples above needs increased by $470 or part of the gain would fall into the lower bracket. Additionally, these all treat the BTC gain as the last part of the Adjusted Gross Income, so the effective rate of the BTC as currency bit would be lower, but the dollar amounts shown above are how much your taxes would be increased due to that income. That having been said, here is a similar example showing tax reductions where the only things that change are that you bought one BTC for $500 and you bought a $30 item for 1 BTC over a year later (so in these cases, again, the minimum adjusted gross income needs increased by $470 or part of the savings from the loss falls into a lower bracket):
Adjusted Gross Income: $9075 or less
BTC as Currency (cannot be claimed): $0
BTC as Asset (counts against income rate): -$47
Adjusted Gross Income: $9076-$36,900
BTC as Currency (cannot be claimed): $0
BTC as Asset (counts against income rate): -$70.5
Adjusted Gross Income: $36,901-$89,350
BTC as Currency (cannot be claimed): $0
BTC as Asset (counts against income rate): -$117.5
Adjusted Gross Income: $89,351-$186,350
BTC as Currency (cannot be claimed): $0
BTC as Asset (counts against income rate): -$131.6
Adjusted Gross Income: $186,351-$405,100
BTC as Currency (cannot be claimed): $0
BTC as Asset (counts against income rate): -$155.1
Adjusted Gross Income: $405,101-$406,750
BTC as Currency (cannot be claimed): $0
BTC as Asset (counts against income rate): -$164.5
Adjusted Gross Income: $406,751+
BTC as Currency (cannot be claimed): $0
BTC as Asset (counts against income rate): -$186.12
So, given that you have to keep track either way, why on Earth would you want BTC treated as currency? Even if some of my information were wrong, treating it as currency would never reduce your taxes more than treating it as an asset, but treating it as currency would still certainly increase your taxes more in some cases that are likely to far exceed the amounts saved where you don't have to report gains under $200. Also, don't forget there are tax structuring laws, so don't think you can gain $200 repeatedly on a regular basis and never have to report it by making small transactions, because that won't fly in most cases.
ETA: I am not an accountant and the information contained in this post is not to be construed as financial advice. This post consists solely of personal opinions and links referencing information used to form those opinions.