Tools

USD Idle Cash Yield Calculator

Idle US dollars can earn very different amounts depending on where you park them. Enter an amount and a holding period, and this tool puts a USD demand deposit, a USD time deposit, SGOV, IB01, IBKR idle cash and exchange USDT flexible savings in one table, with the interest each earns, the US withholding on SGOV distributions and how far each row is from the highest one.

The rates are snapshots taken from posts on this site, each with its date. They change all the time, and you can edit every one of them. Options that pay more usually carry extra layers of risk, and the last column lists what each one adds. This tool only compares numbers; it does not recommend any product and is not investment advice.

Inputs

Amount (US$)Holding period (months)Simple interest, pro-rated by months.

Annual rates (%, editable)

USD demand depositBank of Taiwan posted rate, in effect from 30 Sep 2026.USD time deposit (12 months)Bank of Taiwan posted rate, in effect from 30 Sep 2026; 1, 3 and 6 months pay 2.00%. Breaking a deposit early usually means reduced interest; promotional deposits pay more but come with conditions, see USD time deposit rates in Taiwan compared.SGOV (30-day SEC yield)Published on 1 Oct 2026. The rate is not locked in and moves with short-term rates.IB01 (weighted average YTM)Published on 24 Sep 2026; the table subtracts the 0.07% total expense ratio. YTM does not guarantee future returns; IB01 is accumulating and pays no distributions.IBKR idle cashIBKR rates page, 7 Oct 2026: applies to USD cash above US$10,000 when account NAV exceeds US$100,000; the first US$10,000 earns 0%.USDT exchange flexible savingsPrefilled with the tier-weighted rate of WEEX Auto Earn at the default amount of US$50,000, checked 2026-10-07; the exchange does not say whether it takes a cut of the interest, so this is the rate shown. Changing the amount does not re-weight the tiers; see USDT flexible earn rates compared for current rates.US withholding on SGOV distributions (%)In practice IBKR withholds 30% first and corrects it from January to March of the next year for the share designated as NRA qualified interest income (QII). The QII share varies by year and by distribution, so enter anything from 0 to 30. Only SGOV gets this withholding.

Results

Scroll the table sideways to see every column.

Option	Rate used	Interest for the period	US withholding	After US withholding	Gap to the highest row	What you take on
USD demand deposit	0.60%	US$300	—	US$300	−US$1,745	USD → bank
USD time deposit, 12 months	2.05%	US$1,025	—	US$1,025	−US$1,020	USD → bank; money tied up for the term
SGOV	3.70%	US$1,850	US$555	US$1,295	−US$750	USD → U.S.-domiciled ETF → U.S. Treasuries
IB01	4.09%YTM 4.16% − TER 0.07%	US$2,045	US$0	US$2,045	Highest	USD → Irish UCITS ETF → U.S. Treasuries
IBKR idle cash	2.50%3.13% above US$10,000	US$1,252	—	US$1,252	−US$793	USD → broker cash
USDT exchange flexible savingsPrefilled: WEEX, 2026-10-07	3.54%	US$1,770	—	US$1,770	−US$275	USD value → USDT → Tether → exchange custody → borrowers and leveraged traders

IBKR's 3.13% applies only when account NAV exceeds US$100,000. If your account NAV is not above US$100,000, the actual rate is lower (not modelled here), so the IBKR row overstates the interest.

Interest for the period = amount × annual rate × months ÷ 12. US withholding is calculated for SGOV only; IB01 is accumulating and pays no distributions, so it is 0; the other rows have no US withholding modelled and show no figure. No Taiwan tax is calculated for any row.

This tool only calculates from the rates and inputs you enter and is not investment advice. The rates are snapshots from specific dates and change all the time; yields and YTM are not guaranteed returns, and ETF prices move. Tax, deposit insurance and risk differ by option, so check the latest notices from your bank, broker or exchange before you decide.

How to read the table

"Rate used" is the annual rate actually applied to the whole amount. For IB01 the total expense ratio is already subtracted. For IBKR the first US$10,000 earns nothing, so the rate on the whole amount is below 3.13%: about 2.50% on US$50,000.

The highest row is marked, and the other rows show how many dollars less they earn. The yield measures differ: SGOV's 30-day SEC yield and IB01's weighted average YTM are defined differently, so the gap between them is not a precise gap in future returns.

The last column is each option's risk stack. Any extra yield is paid for taking on those layers; for a way to put each layer in dollar terms, see Where to park idle USD and USDT.

Methodology

Interest for the period uses simple interest pro-rated by months: amount × annual rate × months ÷ 12. There is no compounding and no bank day count (Taishin Bank, for example, calculates USD interest on a 360-day year), so the results are approximate.
USD demand deposit 0.60% and 12-month USD time deposit 2.05%: Bank of Taiwan posted rates in effect from 30 September 2026, from USD time deposit rates in Taiwan compared.
SGOV 3.70%: the 30-day SEC yield on 1 October 2026, from IB01 vs SGOV. The tool uses this figure as it is and does not subtract the expense ratio again.
IB01: the weighted average YTM of 4.16% on 24 September 2026, minus the 0.07% total expense ratio, gives 4.09%. YTM reflects the yield of the bond portfolio the fund holds now and does not guarantee next year's total return.
IBKR idle cash: on the IBKR rates page of 7 October 2026, USD cash above US$10,000 earned about 3.13% when account NAV exceeded US$100,000, and the first US$10,000 earned 0%. Interest = (amount − 10,000) × 3.13% × months ÷ 12.
USDT exchange flexible savings: prefilled when the site is built from the data behind USDT flexible earn rates compared. Only standard flexible products count, not new-user or VIP rates, and data whose latest update failed is left out. Tiered rates are weighted at the default amount, and where an exchange publishes a cut of the interest (OKX keeps 15%, for example), the cut is subtracted.
US withholding on SGOV = interest for the period × the withholding rate. IB01 is an Irish-domiciled accumulating ETF that pays no distributions, so it is 0. No US withholding is modelled for the demand deposit, the time deposit, IBKR cash interest or USDT savings; their tax treatment is a separate question.
No Taiwan tax is calculated. For the overseas income rules see Overseas income and Taiwan's alternative minimum tax: overseas income under NT$1,000,000 per household per year is not counted in basic income; at or above NT$1,000,000 all of it counts; with basic income up to NT$7,500,000 there is generally no basic tax.
Negative or empty inputs count as 0, and the withholding rate is capped at 100%.

What is not included

ETF price changes: SGOV and IB01 prices move slightly every day; the tool only uses the yield to estimate interest.
Commissions and bid/ask spreads. For example, IBKR Pro Fixed charges US$0.005 per share with a US$1 minimum per order, see IB01 vs SGOV.
Currency conversion, and the cost of wiring dollars to a broker and withdrawing them. See the transfer frequency calculator and the cost of withdrawing from an overseas broker to Taiwan.
The risks of USDT itself, exchange custody and the lending market.
Deposit insurance: deposits at Taiwanese banks, including foreign currency deposits, are insured up to NT$3 million per depositor per bank; ETFs at an overseas broker and USDT on an exchange are not covered by Taiwan's deposit insurance.
Rate changes: every rate in the table is a snapshot. A time deposit's rate is set in the contract; the other rates move with the market.
Breaking a time deposit early usually means reduced interest; the tool assumes you hold it to maturity.
Exchange rates: a stronger or weaker US dollar against the NT dollar affects every row the same way, and the tool does not model it.

FAQ

Where do idle US dollars earn the most interest?

With the default snapshot (US$50,000 for 12 months) and before US withholding, IB01 after its expense ratio is about 4.09%, SGOV 3.70%, IBKR idle cash about 2.50% on the whole amount, the USD time deposit 2.05% and the USD demand deposit 0.60%, while USDT savings depend on exchange rates at the time. The yield measures differ and the rates change, and the higher-paying options add ETF, broker, stablecoin or exchange risk. This is a comparison, not a recommendation.

Is 30% withheld from SGOV distributions?

Not necessarily. Nonresidents often have 30% withheld on U.S.-source dividends, but the part of an SGOV distribution designated as NRA qualified interest income (QII) may qualify for an exception. In practice IBKR withholds 30% first and corrects it from January to March of the next year. The QII share varies by year and by distribution, so the tool lets you enter anything from 0% to 30%.

How is interest on IBKR idle cash calculated?

On the IBKR rates page of 7 October 2026, when account NAV exceeds US$100,000, USD cash above US$10,000 earns about 3.13% a year and the first US$10,000 earns 0%; with a lower NAV the rate is lower. For example, with US$50,000 in cash: US$40,000 × 3.13% ≈ US$1,252 a year, about 2.50% on the whole amount. Interest is calculated daily and paid monthly.

How much more does IB01 earn than a USD time deposit?

With the defaults of US$50,000 for 12 months: IB01 at a 4.16% YTM minus its 0.07% expense ratio is about 4.09%, or about US$2,045 a year; a Bank of Taiwan 12-month USD time deposit at 2.05% pays about US$1,025, a gap of about US$1,020. But YTM is not a guaranteed return, IB01 needs an overseas brokerage account and a wire transfer, and it is not covered by Taiwan's deposit insurance, while a time deposit's rate is set in the contract.

Why does the table leave out Taiwan tax?

Every household's income is different. For Taiwan tax residents, overseas income under NT$1,000,000 per household per year is not counted in basic income, and at or above NT$1,000,000 all of it counts; with basic income up to NT$7,500,000 there is generally no basic tax. Details and worked examples are in our post on overseas income and Taiwan's alternative minimum tax.