JAKARTA: Rising interest rates are driving up funding costs and squeezing the net interest margin (NIM) of banks, with analysts saying lenders will need to step up operational efficiency to sustain profitability.
Banks’ interest margins narrowed to an average of 4.34% in June, down from 4.36% in May and 4.48% in June 2025, Financial Services Authority (OJK) data show.
Analysts attributed the decline to the fact that funding costs have risen faster than interest earnings.
In May, Bank Indonesia (BI) raised its benchmark rate for the first time in months to defend a weakening rupiah, lifting it by 50 basis points to 5.25%.
The central bank subsequently announced more rate hikes in June, bringing the BI rate to its current level of 5.75%.
The increase has weighed on domestic banks like the country’s largest private lender, BCA, as well as state-owned Bank Mandiri and Bank Tabungan Negara (BTN), all of which posted lower NIMs in their recent financial reports.
BCA saw its interest margin decline to 5.3% in June from 5.8% a year earlier.
BCA director and chief financial officer Vera Eve Lim said the decline was in “line with the industry trend” amid “competition” among banks that were also seeking to boost credit growth.
She explained that banks had lowered their lending rates as the central bank eased its benchmark interest rate over the last year, but BI’s recent hikes had strained NIMs and compelled banks to make adjustments.
“The decline in the NIM in the first half of this year (1H26) is a consequence of the previous adjustments to lending rates amid the competition in the industry that remains quite intense,” she told a virtual press conference on July 28.
Meanwhile, Mandiri has revised its NIM projection for this year to fall within the range of 4.3% to 4.5%, down from 4.5% to 4.7% previously.
Mandiri’s consolidated NIM dropped to 4.56% in the first semester of this year from 4.7% a year earlier, which the company said primarily reflected lower loan yields from “continued repricing, particularly in the corporate, micro and payroll portfolios, with only a modest increase in funding costs”.
At the same time, tight liquidity conditions so far this year led to a modest increase in the bank’s cost of funds for deposits to 2.04% in the second quarter (2Q) from 1.97% in the 1Q, primarily due to higher time deposit pricing.
BTN, which focuses on housing finance, recorded an NIM of 3.5% in June, a drastic fall from 4.4% in June 2025.
All three lenders reported growing net profit, with that of BCA up 1.8% year-on-year (y-o-y) at 29.5 trillion rupiah, Mandiri’s rising 24.2% y-o-y to 30.4 trillion rupiah and that of BTN increasing 40.8% y-o-y to 2.40 trillion rupiah.
However, the NIM pressure is projected to continue into 2H26, with analysts stressing the need for operational efficiency to prevent the interest margin from eroding profitability.
“It seems that pressure is likely to continue, because if banks were to raise lending rates in this situation, it would increase credit risks,” Trioksa Siahaan, head of research and product development at the Indonesian Banking Development Institute told The Jakarta Post on Monday.
In addition to improving operational efficiency, he said banks should reduce the cost of funds by increasing the share of low-cost deposits.
Doddy Ariefianto, banking analyst at Binus University, said that banks’ NIM declined as funding costs rose faster in response to higher interest rates, tighter liquidity, as well as intensifying competition for third-party funds and for lending.
He expects it would continue to deteriorate in 2H26 or “at least move sideways”, while noting that the potential for recovery remained limited.
Doddy argued that banks should not only pursue a higher NIM, but also maintain sustainable profitability through digital banking, payroll, transaction banking and a stronger financial ecosystem.
He added that banks should grow fee-based income to reduce reliance on interest margins, such as through digital transactions, wealth management, trade finance and other services.
Addressing concerns over heightened competition for deposits in the banking industry, OJK head Friderica Widyasari Dewi emphasised in a press conference on Monday that banks still had ample liquidity, noting that both the ratio of liquid assets to non-core deposits and the ratio of liquid assets to third-party funds remained above pre-pandemic levels. — The Jakarta Post/ANN
