On the same day, September 11, Vietnam's money market showed two prices that seem impossible to reconcile. On the interbank market, banks lent each other overnight funds at just 1.5% a year.Thanh Nien That same day, one Big 4 branch in Hanoi was quoting 8% a year to depositors opening a 6-month savings account.VietNamNet A gap of more than 5x between those two prices isn't a paradox. It's a signal that the yield curve is steepening fast, and the story behind it deserves more than a routine "net liquidity drain" headline.
The subtraction behind the net-drain headline
On September 11, the State Bank of Vietnam (SBV) offered loans on its repo channel across three tenors: 7 days, 35 days and 91 days. Commercial banks took just VND 1,699 billion at the 7-day tenor, priced at 4.5% a year; the two longer tenors found no takers. The same session, VND 39,316 billion of older loans came due for repayment.Nguoi Quan Sat Subtract one from the other and you get VND 37,617 billion in net liquidity withdrawal, the number that drove this afternoon's headlines.
Read the arithmetic closely, though, and the story looks different: the SBV did not actively pull any extra cash out of the system beyond the loans that happened to mature. The central bank kept the window open at all three tenors; commercial banks simply didn't show up to borrow. The reason sits right there on the price tag: repo borrowing costs 4.5% a year, while the same-day interbank rate for overnight funds was just 1.5%.Thanh Nien When you can borrow from a peer bank at a third of the price, you don't go back to the central bank's counter. The net-drain figure, then, is a symptom of surplus liquidity, not the cause of it.
Early-September's spike was a calendar story
This rate gap only formed over the past week. Right after the National Day holiday, on September 3, the overnight rate jumped from a base of 1.19% on August 28 to 6.01%.Nguoi Quan Sat The cause was the holiday calendar, not the underlying capital flows: the two closed days of September 1-2 crammed the system's entire payment demand into the first few sessions after reopening, right when overnight funding accounted for 96% of total VND trading volume, averaging VND 914,756 billion a day in the week of August 31-September 4.VietNamNet A few days of congestion at exactly that tenor was enough to push the price up fivefold.
The SBV responded by injecting roughly VND 10,787 billion net over the first two sessions of the month, all of it at the 7-to-91-day tenors priced at 4.5%.Nguoi Quan Sat Once the payment rhythm normalized, banks let the congestion-relief loans mature without renewing them, which is exactly the VND 39,316 billion that came due on September 11. But if the calendar effect were the whole story, rates should have simply returned to their old base around 1.2-1.5%, not held there session after session. The rest of the explanation comes from a regulatory change that took effect in early August.
One line in the LDR formula got loosened
On July 30, 2026, the SBV issued Decision 1743/QD-NHNN, raising the share of the State Treasury's term deposits counted in the loan-to-deposit ratio (LDR) denominator from 20% to 50%, effective from August 1, 2026 through July 31, 2028.VnEconomy This isn't new money entering the system. Treasury deposits stay exactly where they were; only how they're counted in the compliance formula changed. But the effect is real, because most of that money sits in one place: the four state-owned commercial banks hold more than 99% of all Treasury deposits in the system, with the balance at this group reaching VND 715,630 billion at the end of Q2 2026.CafeFFireAnt
Term deposits at Vietcombank, BIDV and VietinBank alone stood at nearly VND 554,000 billion at the end of June. Under the old 20% rule, only about VND 110,800 billion counted toward the LDR denominator; under the new 50% rule, that figure rises to roughly VND 277,000 billion, adding about VND 166,000 billion to the denominator.FireAnt As the denominator expands, the LDR ratio falls without banks needing to raise a single extra dong in deposits. That matters because at the end of Q1 2026, this group's LDR sat right at the 85% ceiling: Vietcombank at 84.54%, VietinBank at 83.48%, Agribank at 83.28% and BIDV at 82.94%.Bao Moi Mirae Asset Securities estimates the change frees up roughly VND 190,000 billion of extra lending room for the system.Nguoi Quan Sat With less pressure to scramble for overnight funds just to stay compliant, the overnight rate came down with it.
Cheap money lasts only one night
This is where the picture shifts. The 1.5% figure only applies to the overnight tenor. On that same September 11, the 1-week rate stood at 3%, 2-week at 3.8%, 1-month at 5.5%, and 3-month climbed all the way to 7.35%.Thanh Nien Borrowing for three months costs nearly 5x the overnight rate. A curve that steep is telling you the system has a surplus of cash for today and a shortage of it for the quarter ahead. The abundant liquidity the headlines describe is overnight liquidity, not seasonal liquidity.
The medium-term backdrop hasn't reversed either. Per SSI Research, as of August 22, system-wide deposit growth reached 7.97% year-to-date, still below credit growth of 9.71%, though on a VND-only basis deposits have edged ahead of credit.Nguoi Quan Sat Credit still has ground to cover: system-wide outstanding loans as of August 18 were up 9.2% from the end of 2025, against a full-year target of roughly 15%.Tin Nhanh Chung Khoan Capital is moving fast into credit, and the long-term funding needed to feed that flow hasn't caught up.
It's also worth stating plainly that cheap interbank liquidity doesn't automatically flow into other asset markets. On the same September 11 session, the VN-Index fell 1.86% to 1,795.21 points, with 304 decliners against 52 advancers. Cheap overnight money is a bank balance-sheet story, not an equity flow story.
Why savings rates aren't following the interbank rate down
Depositors often expect a falling interbank rate to pull deposit rates down with it. But on that same September 11, a string of deposit rates moved in the opposite direction. A VietNamNet survey at a Big 4 branch in Hanoi found the 8% counter rate now kicks in at the 6-month tenor with balances starting from VND 100 million, down from a previous threshold of VND 1 billion.VietNamNet On published rate sheets, all four Big 4 banks now offer 6.6% a year for 6-9 month terms and 6.8% for 12-18 month terms.
Among private banks the increase is even sharper: VPBank adds 2.5% a year for member-tier customers depositing VND 1 to 300 million, pushing the effective rate up to 8.7% at 6-13 month terms; SCB raised its 13-month deposit rate from 3.9% to 8.7%.Thanh Nien The two prices aren't in conflict, because they're buying two different things: overnight borrowing patches a same-day funding gap, while a 12-month deposit is stable capital for medium-term lending, exactly what the system is short of while credit keeps outrunning deposits. Tonight's cheap money can't substitute for next year's funding.
What to watch
The single most useful number for anyone weighing where to deposit money is the 3-month interbank rate, currently 7.35%, set alongside their own bank's 6-12 month deposit rate sheet. As long as the 3-month tenor stays anchored above 7%, banks will keep paying up for funding longer than overnight, and retail deposit rates are unlikely to follow the overnight rate down.
A genuine reversal signal would arrive if the 3-month tenor falls back toward the 5% range at the same time deposit growth overtakes credit growth for several consecutive months. Until both conditions show up together, the 6.6-6.8% range on Big 4 rate sheets remains the reasonable benchmark for terms of 6 months or longer. Rates above 8% currently come attached to specific balance or membership-tier conditions, worth reading closely before comparing across banks.