Non-Singapore-Dollar Tax Computations: Conversion Rules and Complete Examples

Edition, scope and the insurer exception

This article follows the twenty-five-page third edition published on 30 January 2026. Earlier editions appeared on 29 June 2012 and 12 August 2024. A business using a non-S$ functional currency in its financial statements should use that currency for its tax computation, subject to the separate S$ return requirements. Functional currency reflects the main economic environment, not a convenient filing preference.

Section 62B and the Income Tax (Functional Currency) Regulations 2004 underpin the rules. Their early application was YA 2004 for a period beginning on 1 January 2003 and YA 2005 for periods beginning later, with earlier specific approvals preserved. Section 62B does not apply to Singapore-licensed insurers for accounting periods beginning on or after 1 January 2023; their FRS 117 guide governs the separate regime. Sole proprietors and partnerships may also use non-S$ financial statements, certified by the proprietor or precedent partner.

How far each computation stays in functional currency

A company computes through chargeable income after partial/full exemption in its functional currency. A partnership computes distributable profit, loss, other income and capital allowances that way. A sole proprietor computes adjusted trade profit/loss before losses brought forward, together with trade capital allowances, that way. The relevant results are then converted to S$ at the YA average rate. Tax returns and their appendices remain in S$ even though the supporting computation is non-S$.

Existing balances and the two irrevocable choices

Existing S$ balances include unused capital allowances, trade losses/further deductions, donations and investment allowances; existing assets’ tax written-down values and original costs where allowances have been granted; and earlier income/expense amounts becoming taxable or deductible later. A newly incorporated company using non-S$ from incorporation has no earlier S$ computation balances of this kind.

At the first non-S$ filing, elect irrevocably between the changeover-rate and average-rate methods. The changeover rate is the mean of monthly-end rates over the twelve months before the last S$ accounting-period end. The average rate is the mean of monthly-end rates in the relevant YA basis period. Use MAS rates or another rate considered reasonable by the Comptroller. For YA 2021 with basis period calendar 2020, these are calendar 2019 and calendar 2020 respectively.

Table 1: what gets carried forward under each method

With the changeover method, convert existing S$ balances once; compute current allowances and deductions in functional currency and carry unused converted balances forward in that currency without repeating translation. With the average method, convert using the YA rate, compute deductions, then translate unused balances back to S$ at that same rate for carry-forward; repeat this cycle in subsequent YAs until the original balances are used.

Original asset costs must also be translated for balancing charges or allowances. Do not confuse tax written-down value, the unrelieved cost, with the original cost needed for another calculation. The same chosen method also translates earlier unrealised S$ revenue exchange differences when they later become taxable/deductible.

Current-year items and currency-change differences

Other current-year company items already in functional currency need no additional conversion: adjusted trading profit/loss, allowances on new assets or building expenditure, interest/dividend/rental income and donations. Further deductions and investment allowances based on current-year expenditure also stay in that currency. Exchange gains/losses arising merely from changing functional currency are not taxable or deductible.

Sections 24 and 25 asset transfers

For an eligible section 24 related-party sale, translate the seller’s tax written-down value into the buyer’s functional currency at the sale-date exchange rate. Relevant control can be buyer over seller, seller over buyer, or a third party over both.

For an eligible section 25 business-conversion transfer without consideration, such as conversion of a firm to an LLP, the parties may elect for the transferee to claim remaining unallowed capital expenditure. If currencies differ, translate tax written-down value at the transfer-date rate. These transfers use transaction-date rates rather than the general annual average.

Group Relief transfers and assessment revisions

Qualifying current-year losses, allowances and donations transfer out in the transferor’s functional currency. If the claimant uses another currency, convert at the YA average rate. If a revised claimant assessment reduces the claim, the excess is retained by the transferor in its own functional currency. Group Relief qualification and ordering conditions still apply separately.

Revenue exchange differences and a date discrepancy

From YA 2004 the normal revenue-exchange regime follows accounting unless the YA 2004 opt-out was made; old unrecognised amounts were deemed realised at transition. Existing S$ amounts becoming taxable or deductible after a functional-currency change use the existing-balance translation method.

Footnote 11 in this functional-currency PDF dates the option to revoke the old opt-out to 12 November 2008. The dedicated foreign-exchange sixth edition instead expressly states 12 November 2018. This is a source discrepancy, not a new choice between two commencement dates. Consult the linked dedicated guide and confirm the applicable election details with IRAS rather than repeating the conflicting footnote as settled guidance.

Incentive base income, exemptions and tax payable

Convert an incentive’s S$ base-income amount into functional currency at the relevant YA average rate. Do the same for partial/full exemptions under sections 43(6A), 43(6B) or 43(6D). Company tax is ultimately S$: multiply functional-currency chargeable income after exemption by the corporate rate, then translate at the YA average. The exemption conversion rate remains the YA average even where existing balances use the changeover method.

Foreign tax credits, withholding and dividend vouchers

Double-tax relief and unilateral credit are limited to the lower of Singapore tax on the foreign income after allowable deductions and the foreign tax paid. Convert both amounts to S$ at the same YA average rate; the foreign amount may be actual payment or the amount reflected in the financial statements. Singapore tax withheld on loan-stock interest or REIT distributions is credited at its actual S$ withheld amount.

A resident company paying a non-S$ dividend gives the S$ equivalent on the voucher/notification where applicable using the payment-date rate. A recipient converts the stated S$ equivalent into its own functional currency at its YA average, even where payer and recipient use the same non-S$ currency. S$ loan-stock interest with source deduction is likewise converted at the recipient’s YA average.

Partnerships and partners

Company rules generally apply to partnerships, except Group Relief, company tax incentives, company exemptions and company tax payable. The precedent partner elects the existing-balance method irrevocably with the first non-S$ return; partnership-level balances exclude unused tax items because those belong to partners. Allocate profit/loss/other income and allowances, then convert each partner’s share to S$ at the average rate. A partner’s unabsorbed loss or allowance is carried forward or back in S$ under the applicable rules.

Sole proprietors and personal reliefs

The sole proprietor makes the initial written, irrevocable conversion-method election for existing balances, excluding unused tax items. Convert current adjusted profit/loss and trade allowances into S$ at the average rate, then offset earlier S$ losses. Current S$-converted losses/allowances may offset other income and any unused amount remains in S$ for carry-forward/back. Foreign-source income is translated at the average rate; tax credits and personal reliefs are computed in S$. Actual Singapore source withholding remains credited in S$.

Annex A: complete changeover-rate company example

ABC first files in US$ for YA 2021, with 31 March year-end. The April 2018–March 2019 changeover rate is S$1.37/US$ and April 2019–March 2020 average is S$1.36/US$. US$100,000 profit is reduced by US$21,898 brought-forward allowances (S$30,000/1.37), US$36,496 old-asset allowances (S$50,000/1.37) and US$10,000 new-asset allowances, leaving US$31,606. Deduct old losses US$18,248 (S$25,000/1.37), add interest US$10,000, deduct donation US$1,200 and investment allowance US$11,111: income before exemption is US$11,047.

The appendix exempts US$7,362: US$5,515 on the first US$7,353 at 75%, plus US$1,847 on the remaining US$3,694 at 50%. Taxable income is US$3,685; the illustrated tax is US$3,685 × 17% × 1.36 = S$851.97. The EDB-approved S$90,000 investment cost at 30% is converted to US$65,693, with US$19,708 potential allowance; current qualifying spending US$37,037 gives US$11,111. Overall S$ allowance cannot exceed S$27,000. Remaining old-asset value stays in US$ under this method.

Annex B: complete average-rate company example

With the same US$100,000 profit and S$1.36/US$ average, old S$30,000 allowances become US$22,059, old-asset S$50,000 allowances become US$36,765 and new allowances are US$10,000. The remainder is US$31,176. Old S$25,000 losses become US$18,382, leaving US$12,794; add US$10,000 interest, deduct US$1,200 donation and US$11,111 investment allowance, giving US$10,483 before exemption.

The exemption is US$7,080: US$5,515 on the first US$7,353 plus US$1,565 on US$3,130. Taxable income US$3,403 produces S$786.77 at 17% and 1.36. The S$90,000 approved cost becomes US$66,176 and 30% is US$19,853; current US$37,037 spending again claims US$11,111, subject to S$27,000 overall. Remaining old balances return to S$ at the same YA rate and are reconverted at the next YA rate.

Annexes A and B: keep the example’s limits separate

Both appendix notes describe S$100,000 as the maximum chargeable income qualifying for partial exemption. That limit wording is part of the example source and should not be presented as the current general PTE ceiling. The small income amounts in these calculations fall within the first bands, so the displayed computations above preserve the PDF results without adopting that note as a general rule. The annex also assumes YA 2021 treatment/rate follows YA 2020 and does not add unrelated present-year rebates.

Annex C: new company and Group Relief ordering

DEF has US$10,000 interest, US$20,000 current allowances and US$100,000 adjusted trade loss for YA 2021; its calendar-2020 rate is S$1.38/US$. Related claimant X has S$53,400 assessable income, equivalent to US$38,696. First use allowances against DEF’s interest, leaving US$10,000 allowances. Transfer those first, then US$28,696 trade losses to X. DEF has no chargeable income and carries US$71,304 trade loss forward to YA 2022 in US$. The companies were incorporated on the same date and satisfy Group Relief qualification in the example.

Annex D: the complete sole-proprietor calculation

XYZ uses US$ and a 31 December year-end; his partnership uses euro. The 2019 changeover rate is 1.36 and 2020 average is 1.38 S$/US$. The printed appendix deducts US$22,059 of old S$30,000 allowances, US$36,765 of old-asset S$50,000 allowances and US$10,000 new allowances from US$100,000 profit, leaving US$31,176. It converts that to S$43,023, deducts S$25,000 old losses and reaches S$18,023 trade income.

Add S$100,000 partnership share (one fifth, converted from euro at the average), S$100,000 employment and S$10,000 interest: S$228,023. Less S$1,200 donation gives S$226,823 assessable income; S$50,000 reliefs gives S$176,823 chargeable income. The historical YA 2021 tax is S$13,950 on S$160,000 plus 18% of S$16,823, totalling S$16,978.14. Remaining old-asset US$36,765 stays in US$ with changeover, while under average it would revert to S$50,000 for next-year conversion.

Annex D qualification and filing checklist

The printed Annex D converts brought-forward allowances into US$, while paragraphs 5.34–5.36 say the proprietor’s existing-balance election excludes unused tax items. Retain this discrepancy when explaining the printed calculation; do not turn it into an unconditional instruction to reconvert every proprietor’s brought-forward allowance. Verify treatment of that specific item before using the example for a return.

Keep the functional-currency determination, first-year written election, prior S$ balances, rates, conversion workings, exemption calculations and S$ return figures. Use transaction-date rates for the specified asset transfers/dividend payments and YA averages for the other listed items rather than one rate everywhere.

Amendments and enquiry routes

The August 2024 revision removed obsolete incorporation-date and imputation-dividend references, added the insurer exception and section 25 transfers, updated withholding/REIT material and refreshed examples. The current third edition is dated January 2026. The PDF lists 1800-356 8622 for corporate and 1800-356 8300 for individual enquiries. All four annexes are explained here; the original PDF and supplementary foreign-exchange guide remain linked.