Float arbitrage
Promo APR vs. keeping cash invested
Ride the 0% offer, leave the cash earning yield, pay minimums, settle in full before the promo ends. Net benefit is what’s left after payoff.
mo
%
$/yr
%/mo
of balance, paid monthly% APY
%
%
%
T-bill interest is exempt from state tax — fed rate only.
Net benefit over 12 months
best: —
HYSA @ 3.0%
—
T-bills @ 3.5%
—
Cumulative net benefit by month
T-bills
HYSA
Assumptions.
Minimums are paid from the invested cash monthly; the remaining balance is paid in full in the final promo month.
Interest compounds monthly at APY/12. T-bill figure assumes rolling bills at a constant yield.
No late-payment or deferred-interest scenarios modeled — miss the payoff date on a deferred-interest offer and the math inverts badly.