The primary bank used to be easy to identify: it was usually where salary arrived, bills were paid and the largest balance sat. Open banking and multi-account behaviour are making that definition less reliable.
For decades, the primary banking relationship was treated as a largely static fact. The account that received salary, held the main current-account balance and carried the household's direct debits was assumed to be the customer's financial centre of gravity. That assumption is becoming harder to defend. Consumers can now hold several accounts, route spending through a digital wallet, leave savings elsewhere, initiate payments through third-party apps and switch a current account with far less operational friction than in the past.
The result is a distinction between account ownership and account centrality. A bank may remain the nominal home of a current account while losing the flows that make the relationship economically important. Conversely, a bank with only a modest average balance may still be central if it receives recurring income, handles bills, originates payments and remains connected to the customer's wider financial activity.
This article uses 'account centrality' as an analytical framework rather than a formal regulatory or industry metric. The idea is simple: customer primacy may increasingly be measured by the share and persistence of financial activity that passes through an account, not merely by the balance recorded at month-end.
Switching is becoming easier, but primacy is not the same as switching
The UK provides one of the clearest tests of the old model. The Current Account Switch Service reported 319,529 switches in the first quarter of 2026, a 43% increase from the same period a year earlier. Over the 12 months to March 2026, the service processed more than 1.15 million switches, while 99.8% of switches were completed within the seven-working-day timescale.
By July, the service was reporting a 39% year-on-year rise in first-half switching. The implication for banks is not simply that customers are more willing to move. It is that switching data identify a discrete event, while relationship erosion can happen without a formal switch at all. A customer can leave an old account open, redirect salary, move card spend and transfer savings elsewhere. From an economic perspective, the bank may have lost primacy before the account is ever closed.
Open banking separates the financial interface from the balance sheet
Open banking accelerates this separation. In July 2026, Open Banking Limited reported more than one billion open-banking payments and 100 billion API calls across the UK's largest account providers since launch. June alone recorded 40.16 million open-banking payments, while reported user connections stood at 18.81 million.
The government's Smart Data 2035 strategy noted that UK open-banking adoption had already exceeded 17 million users in January 2026, up from 7.7 million in August 2023. The FCA's April 2026 open-finance roadmap goes further by setting a path toward broader data portability across financial products by 2030.
These developments weaken the old assumption that the bank holding the account must also own the customer interface. A budgeting app can become the place where a consumer sees all balances. A third party can initiate payments. A lending decision can draw on transaction data held elsewhere. Primacy therefore becomes less about exclusive ownership of data and more about whether the institution remains the default route for money movement, liquidity and financial decisions.
Payment flows may reveal more than average balances
A central account tends to display several recurring characteristics. Income arrives into it. Essential bills leave from it. Card or wallet funding originates there. The customer returns to it after large transfers. The account remains active across weeks and months rather than only around a promotional rate or one product event. None of those signals is definitive on its own, but together they can describe the operational role of the account more clearly than average balance alone.
The scale of everyday payments reinforces why flow data matter. The European Central Bank reported 83.5 billion non-cash payments in the euro area in the second half of 2025, up 6.9% year on year. Cards accounted for 57% of the number of transactions, credit transfers 21% and direct debits 14%. An account that remains embedded in those recurring payment patterns can be economically important even if surplus savings are held elsewhere.
The economics of primacy are broader than deposit funding
For banks, centrality matters because the primary relationship can influence several revenue pools at once: deposit funding, card spend, overdraft usage, payment fees, lending opportunities, financial advice and cross-selling. But those economics are increasingly disaggregated. A customer may keep deposits with one bank, borrow from another, use a third provider's app and pay through a wallet. The institution with the largest balance is not necessarily the institution with the strongest relationship.
That changes how customer profitability should be interpreted. A low-balance current account that sits at the centre of salary, bills and transfers may be more strategically valuable than a higher-balance account used mainly as a temporary cash store. Conversely, a large balance accumulated because of a short-term savings rate can overstate relationship depth.
A useful metric would need to be multidimensional
A practical account-centrality framework could combine recurring income share, outgoing payment share, direct-debit persistence, card-spend activity, frequency of account access, open-banking connections, recovery after large outflows and the proportion of the customer's total known liquidity held with the institution. The weighting would differ by segment: a salary account is meaningful for a retail customer, while collections, payroll and supplier payments matter more for an SME.
The objective should not be to create a single universal score. It should be to distinguish between three states that traditional customer labels often blur: an account that is open, an account that is active, and an account that is genuinely central to the customer's financial life.
The counterargument: centrality can be noisy and privacy-sensitive
There are important limitations. Open-banking connections reveal only the data a customer has consented to share. A household can deliberately separate bills, spending and savings across several accounts, making any attempt to identify one 'primary' bank artificial. High transaction volume can also reflect low-value activity rather than relationship depth, while a quiet account may still hold strategically important emergency savings.
There is also a governance boundary. Transaction data are highly revealing. Using them to measure relationship strength requires clear purpose limitation, explainability and data-access controls. Banks should avoid turning account centrality into an opaque behavioural label that affects pricing or eligibility without a defensible customer outcome.
Centrality may become a product-design signal
Once banks distinguish account activity from account centrality, product design can change. A bank that knows it is the customer's salary and bill-payment hub may not need to compete for every marginal savings pound at the highest available rate. It can instead focus on reliability, cash-flow tools, overdraft design, rewards and service features that reinforce the account's operating role. A bank that holds savings but sees little transactional activity faces the opposite problem: it may have funding without a deep relationship and therefore greater exposure to rate-led movement.
The distinction also affects retention economics. Conventional churn models often look for account closure or balance decline. A centrality model can detect softer signals earlier: salary redirected elsewhere, direct debits falling away, card spend declining, open-banking connections disappearing or incoming transfers no longer replenishing the account. None of those events proves that a customer is leaving, but together they can show that the relationship is becoming less central before a formal switch occurs.
SME banking makes the distinction even clearer
For small businesses, the primary relationship is often visible through operating flows rather than balance size. Collections, payroll, tax payments, supplier transfers and merchant settlements can make one account operationally critical even when excess cash is swept to another provider. The Current Account Switch Service recorded 7,915 small-business and charity switches in the first quarter of 2026, while its 2025 SME analysis highlighted continued demand for digital tools, cost-effective banking and relationship-led support. That combination suggests that primary-bank status in business banking is increasingly earned through workflow relevance as much as through deposit capture.
This matters for credit as well. A lender that sees the operating account may have a richer view of cash generation, seasonality and payment behaviour than a lender that sees only periodic financial statements. Open finance can broaden that visibility across institutions, reducing the information advantage of the incumbent. The competitive response is therefore not simply to own more data, but to remain useful enough that customers continue routing activity through the bank.
Evidence versus inference
The evidence is strong that switching has become easier, open-banking use has expanded materially, and payment activity is increasingly distributed across multiple providers and interfaces. It is also clear that formal account closure is no longer the only way a customer can shift financial activity away from a bank.
The inference is that account centrality will become a more useful measure of customer primacy than balance or product count alone. No regulator currently prescribes a standard 'centrality' metric, and the relationship between transaction share and long-term profitability will differ across institutions. The framework is therefore best used as a strategic and analytical lens rather than a formal prudential measure.
What it means for banks and fintechs
For incumbent banks, the competitive task becomes protecting the flows that make an account central: salary, collections, recurring bills, card spend and trusted access. For challenger banks, gaining centrality can matter more than merely gaining account openings. For fintechs and open-finance providers, the opportunity lies in orchestration: helping customers manage several financial relationships while making permissions, data quality and consent transparent.
The broader implication is that the primary banking relationship is becoming behavioural rather than administrative. The bank that matters most may increasingly be the one through which the customer's financial life actually moves.
Conclusion: primacy is becoming a flow, not a label
Banks will continue to count accounts, balances and products because those measures remain fundamental. But in a world of easier switching, open APIs and multi-banking, they no longer tell the whole story. Customer primacy is becoming visible in the persistence and direction of financial flows.
That makes account centrality a useful next-generation question: not simply 'does this customer bank with us?', but 'how much of the customer's financial life still depends on us?' The answer may prove more valuable than the balance on any single day.
References
1. Current Account Switch Service — Q1 2026 switching data
2. Current Account Switch Service — Switching data, July 2026 update
3. Open Banking Limited — One billion payments and 100 billion API calls, 30 July 2026
4. Open Banking Limited — API performance statistics
5. UK Government — Smart Data 2035 Strategy, 26 March 2026
6. Financial Conduct Authority — Open finance roadmap, 14 April 2026
7. European Central Bank — Payments statistics: second half of 2025, 22 July 2026
8. Current Account Switch Service — 2025 switching results, 29 January 2026