Dimplo decision sheet
The highest advertised yield is not always the best home for short-term cash. Match each dollar to its deadline, access requirement, insurance or government backing, and after-tax return.
Interactive estimate
Short-term cash yield comparison calculator
Compare a savings APY with a Treasury bill yield for a known holding period. This is a dollars-and-access screen, not a recommendation or a live-rate quote.
Estimated interest for this period
--savings after estimated state tax
--T-bill before federal tax
--estimated T-bill difference
Savings interest and Treasury interest are generally federally taxable. This simplified screen applies the state-tax difference only, because U.S. Treasury interest is generally exempt from state and local income tax. It does not model purchase price, exact bank compounding, fees, or an early sale.
1. Give the money a job
| Cash purpose | Amount | Earliest need date | Notice before use | Must not lose principal? |
|---|---|---|---|---|
| ________________ | $______ | ________ | Same day / days / known date | Y / N |
| ________________ | $______ | ________ | Same day / days / known date | Y / N |
| ________________ | $______ | ________ | Same day / days / known date | Y / N |
2. Match the access pattern
| Option | Usually fits | Access issue | Protection to verify | Tax note |
|---|---|---|---|---|
| High-yield savings | Emergency cash and uncertain dates | Transfers may take time; account rules vary | FDIC or NCUA coverage and ownership category | Interest is generally federally and state taxable |
| No-penalty CD | Known holding period with a possible early exit | Withdrawal rules vary and may require closing the CD | Deposit-insurance coverage | Interest is generally taxable as reported |
| Traditional CD | Known date and willingness to accept an early-withdrawal penalty | Penalty can erase part of the yield | Deposit-insurance coverage | Interest is generally taxable as reported |
| Treasury bill held to maturity | Cash with a known four-to-52-week window | Money is less convenient before maturity; broker sale value can change | Direct obligation of the U.S. government, not FDIC insurance | Interest is federally taxable but generally exempt from state and local income tax |
3. Compare dollars, not headlines
For a simple one-year estimate:
Interest dollars = principal x annual yield
Then subtract fees, penalties, and estimated taxes that differ between the choices. For a shorter holding period, multiply by the approximate fraction of a year only as a rough screen; Treasury bill pricing and bank compounding can make the exact result differ.
Worked example
Assume $20,000 can remain untouched for 26 weeks. A savings account yields 4.00% and a 26-week Treasury bill has an investment rate of 4.10%. A rough pre-tax comparison is approximately $400 versus $410 for half a year only if those percentages and conventions are made comparable. The $10 difference is not meaningful if the bill creates access friction or the savings rate changes. The decision starts with the need date, not the ten-dollar spread.
4. Safety checks
- □ I verified the bank or credit union and the legal institution holding the deposit.
- □ I totaled deposits in the same ownership category at the same institution.
- □ I understand the maturity or early-withdrawal rule.
- □ I kept same-day emergency cash outside any locked product.
- □ I recorded the rate and date instead of assuming it will remain available.