The European Central Bank will receive hundreds of billions of euros in prepayments of long-term cheap loans from the banking industry this year.
The central bank has tightened the terms of its liquidity program to help in its fight against inflation.
This month, repayments of the so-called targeted long-term refinancing operations - commonly known as TLTRO - are possible for the first time.
Estimates differ widely on how much of the €2.1 trillion in outstanding funds will flow back in November.
In a Bloomberg survey of economists, the spectrum ranged from 200 billion euros to 1.5 trillion euros.
The median of the estimates was 600 billion euros.
For December it was 285 billion euros.
Banks have until Wednesday to tell the ECB whether they intend to repay this month.
Fighting record inflation, the ECB modified the terms of its lending program last month to ensure it was compatible with its increasingly tight monetary policy stance.
In the pandemic crisis, the TLTROs had helped the banks with liquidity.
The now changed terms have eliminated an arbitrage opportunity that allowed lenders to park cash in the ECB's deposit facility for risk-free income.
Results for the first redemption opportunity will be released on Friday.
"There has always been a great deal of uncertainty in forecasting TLTRO repayments," explained Piet Christiansen, Chief Strategist at Danske Bank.
"This time is no different.
The new terms need to be balanced with year-end liquidity patterns and regulatory factors.” Analysts expect more than €1.6 trillion to be repaid by the end of the second quarter.
The first repayments this year could have a direct impact on the ECB's monetary policy stance, notes ING's Carsten Brzeski.
"Balance sheet reduction (including QT) would become a substitute for rate hikes in 2023," the economist said.