Guam capital gains tax calculator

Guam taxes its residents under the mirror system: the U.S. Internal Revenue Code applies with 'Guam' substituted for 'United States', so the rates are the American ones, paid to the Guam Department of Revenue and Taxation instead of the IRS. A gain on an asset held more than one year is taxed 0%, 15% or 20% depending on your taxable income; a gain on an asset held one year or less is ordinary income at 10% to 37%; and the 3.8% net investment income tax applies by mirror once income passes $200,000 ($250,000 married filing jointly).

A bona fide resident of Guam files the mirrored Form 1040 with the Guam Department of Revenue and Taxation by 15 April, with every payment going to Guam. IRS Publication 570 states that a bona fide resident of Guam files the return with Guam and includes income from worldwide sources, and that a resident who files with and fully pays Guam owes the United States no return.

Capital losses offset capital gains without limit. A net capital loss deducts at most $3,000 ($1,500 married filing separately) against ordinary income each year, and the rest carries forward indefinitely with no time limit.

Guam taxes its residents under the mirror system: the income-tax laws in force in the United States apply in Guam (48 U.S.C. 1421i(a)), are deemed to impose a separate Guam Territorial income tax payable to the government of Guam (1421i(b)), and are read with 'Guam' substituted for 'United States' (1421i(e)). IRS Publication 570 (2025) directs a bona fide resident of Guam to file the return with Guam and include income from worldwide sources, and the Guam Department of Revenue and Taxation (DRT) publishes the mirrored Form 1040 (Guam Individual Income Tax Return) each year at www.guamtax.com.

Long-term capital gains (a capital asset held more than one year, IRC 1222(3)) are taxed 0/15/20 by taxable income. The breakpoints for 2026 are the section 1(j)(5) maximum zero-rate and maximum 15% amounts of Rev. Proc. 25-32: single 49,450/545,500, joint 98,900/613,700, separate 49,450/306,850, head of household 66,200/579,600. The gain stacks on top of ordinary taxable income plus net short-term gain (Schedule D Tax Worksheet order).

The 20% top rate is statutory (IRC 1(h)(1)(D)); IRS Topic 409 states 'a capital gains rate of 20% applies to the extent that your taxable income exceeds the thresholds set for the 15% capital gain rate'.

Net short-term capital gains (held one year or less) are taxed 'as ordinary income at graduated tax rates' (IRS Topic 409); they fill the ordinary brackets, not the 0/15/20 schedule.

The holding-period edge is strict: 'if you hold the asset for more than one year before you dispose of it, your capital gain or loss is long-term', counting 'from the day after the day you acquired the asset up to and including the day you disposed of it' (IRS Topic 409). A sale on the exact first anniversary is short-term.

Capital losses net capital gains without limit; a net capital loss deducts at most $3,000 ($1,500 married filing separately) against ordinary income (IRC 1211(b)) and the excess carries forward to later years without a time limit (IRC 1212(b)).

The 3.8% net investment income tax applies through the mirror: IRC 1411 is part of the Internal Revenue Code that 48 U.S.C. 1421i(a) applies in Guam, and IRS Publication 570 (2025) says the NIIT 'generally does not directly apply' to bona fide residents of Guam (they owe no U.S. federal return) and tells them to seek 'guidance on the possible mirrored application of the NIIT in these jurisdictions' from their territorial tax department. It charges 3.8% of the lesser of net investment income or the excess of modified adjusted gross income over $250,000 joint / $125,000 separate / $200,000 otherwise (IRC 1411(b)).

Wash sales (IRC 1091): a loss on stock or securities is disallowed where substantially identical stock or securities were bought within the 30 days before or after the sale; the disallowed loss adds to the basis of the replacement shares. The statute's words cover stock or securities, not other property.

The main-home exclusion (IRC 121) applies through the mirror: $250,000 of gain excluded ($500,000 on a joint return) on a principal residence owned and used two of the last five years, once every two years.

Not modelled, flagged in the calculator's copy: the 25% rate on unrecaptured section 1250 gain and the 28% maximum on collectibles and section 1202 qualified small business stock.