One of the biggest mistakes people make when switching banks is closing their old account too quickly. You get the confirmation your new account is open, you're excited about the bonus, and then you shut down the old one—only to discover a delayed payment is sitting in limbo, or a direct debit bounced, or you've accidentally triggered a clawback clause in your new account's terms.
February is peak switching season, and plenty of you are right now in the middle of this transition. If you're one of them, or you're planning your switch in the next few weeks, you need to understand how to run both accounts simultaneously. It's not glamorous, but it's the difference between keeping your £150–£500 bonus and losing it entirely.
Why Running Accounts in Parallel Matters
When you initiate a bank switch through the UK's Current Account Switch Service (CASS), the process takes seven working days. But here's the part most people don't realise: the switch doesn't move money retroactively. It moves future payments and standing orders. Anything in transit—payments you made three days ago, deposits coming in tomorrow—can end up in the wrong place if you're not careful.
More importantly, for the purposes of qualifying for a switch bonus, you often need to keep your old account open and active for a full 90 days after the switch completes. Close it early, and some banks will claw back your bonus.
This is the parallel run: the window where both accounts are genuinely open and active, and you need to know what's happening in each one.
The Real Timeline of What Happens
Let's walk through exactly what happens when you switch. You apply for a new account on, say, February 10th. The bank does a credit check (usually a soft check, which doesn't affect your score), and if approved, they send you to CASS.
From the moment you authorize the switch, you have seven working days. During these seven days:
- CASS notifies your old bank
- CASS notifies your new bank
- Your old bank prepares a file of all your standing orders and regular payments
- Your new bank imports these
- Any direct debits are re-registered at the new bank
But here's the trap: this doesn't happen instantly. If a bill payment goes out on day 4 of the switch, it might still go from your old account. If your salary comes in on day 5, it might arrive at your old account before the switch has completed the transfer setup.
That's why the parallel run exists—and why you cannot, under any circumstances, close your old account until you've verified that:
- All standing orders have genuinely moved
- All direct debits are working from the new account
- At least one full pay cycle (usually 30 days) has passed without issues
- The bonus has actually landed
The Direct Debit Minefield
Here's where things get complicated. Direct debits are reregistered during the switch, but "reregistered" doesn't mean "automatically working." Your energy company, water company, insurance provider—they all need to accept the new direct debit mandate.
In February 2026, most major providers will do this smoothly. But some smaller providers, some older accounts, or some regional utility companies can take an extra week or two to process the mandate change. This means in your parallel run, you might have:
- Old account: Still receiving some direct debits
- New account: Receiving others, but not all
The risk is obvious: if you close the old account and a direct debit tries to bounce, you're hit with an unpaid item charge—usually £5–£10 per incident.
What do you do? Keep the old account open, and actively monitor it for the full 30 days after your switch is supposed to complete. Check it every week. It should gradually go quiet as each direct debit transitions over.
Interest During the Parallel Run
Here's something nobody talks about: you might actually be earning interest on both accounts during the parallel run, and you need to track this for tax purposes.
Let's say you switch from Account A (which pays 0% interest) to Account B (which pays 4% interest). During your parallel run, you might leave, say, £3,000 in Account A as a buffer. From the moment the switch completes until you're confident enough to close Account A (which could be 30–90 days), you're earning zero interest on that £3,000.
But here's the nuance: if your new account has a cap on how much balance earns interest, you need to think about where you're keeping what. Some high-interest current accounts pay 4–5% interest, but only on balances up to £1,500. If you're trying to maximize earnings during the parallel run, you need to:
- Keep enough in the old account to cover any stragglers
- Put the rest in the new account, up to the interest cap
- Keep anything over the cap in a separate high-interest savings account
This requires active movement of money and careful tracking. It's not automatic.
The Cooling-Off Complication
If you've started multiple switches (and in February 2026, many people do), your cooling-off periods are stacking up. Each switch has a 30-calendar-day cooling-off period from the day the switch completes. If you're running three parallel switches, you have three different end dates for three different parallel-run windows.
This is why people get confused. It's not "run all accounts in parallel for 30 days." It's "run each pair of accounts in parallel for 30 days from their individual completion date." If you've started switches on Feb 1, Feb 8, and Feb 15, you're not done with your parallel runs until March 15 at the earliest—and that's assuming you don't run into delays.
Keep a spreadsheet. I know it sounds anal-retentive, but in February, when the switching offers are good and people are stacking bonuses, your parallel-run tracking is the difference between a smooth operation and a disaster.
Bonus Clawback: The Hidden Risk
Here's the biggest danger in the parallel run: clawbacks. Many banks specify that you must keep your old account open for 90 days after the switch without closing it. Some banks check not just that the account is open, but that it's active—meaning money is moving through it.
If you switch to a new account on February 15, and you close the old one on February 20, you're in trouble. Even if you don't actually close it yourself, if the old bank closes it due to inactivity, you might trigger a clawback. The bonus disappears, sometimes weeks later, and suddenly you're £200 down without knowing why.
During the parallel run, keep both accounts genuinely active. Make small transfers between them. Keep some direct debits running from the old account, or at least check it weekly so the activity is visible. Some banks look at login frequency—if you're logging in to access the account, it's "active," even if no money is moving.
A Real February 2026 Scenario
Let's say you're doing what a lot of people are doing this month: switching from your primary current account to grab a £300 bonus, while also switching a joint account to get another £300. Here's what your February parallel run looks like:
Week 1 (Feb 1–7): You apply for the first switch and complete the CASS authorization.
Week 2 (Feb 8–14): The switch completes. You now have Account A (old, primary) and Account B (new, primary). You're running both. Your salary comes in—hopefully to Account B, but maybe partially to Account A while the migration settles. Your energy bill comes out of Account B. Your insurance comes out of Account A (because the mandate hasn't switched yet).
Week 3–4 (Feb 15–28): You initiate the second switch on your joint account. Now you have Account C (old, joint) and Account D (new, joint), running in parallel with A and B. You're monitoring four accounts. Your joint direct debits are transitioning. Some work from D immediately. One—maybe your mortgage or rent—is stuck on C for another week.
March (Ongoing): By mid-March, all the direct debits have migrated. You've confirmed no payments are bouncing. But you can't close any of these accounts yet, because the 90-day window for bonus protection hasn't elapsed. You need to wait until mid-May for the first switch and mid-June for the second.
During this time, you're juggling four accounts, managing four sets of direct debits, tracking four interest calculations (if your new accounts pay interest), and ensuring you hit any bonus-qualifying criteria (like maintaining a £1,500 balance in Account B for the bonus terms).
This is the parallel run, and it's why people either get it completely wrong or do it methodically with a system in place.
How to Actually Manage This
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Create a switch tracker. Note the date you authorized each switch, the date it completed, and the date you can safely close the old account (today's date + 90 days minimum).
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Monitor your old accounts weekly. Check that direct debits are gradually moving to the new account. Flag anything that hasn't moved after 30 days.
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Keep old accounts active. Log in to them at least once a week. Don't leave them dormant, or your bank might close them automatically.
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Don't be tempted to move money too quickly. If you're running three parallel switches, you might have £10,000 split across six accounts (three old, three new). Don't consolidate everything into one account until the 90-day window is up.
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Check your bonus terms in writing. Before you close any old account, read your new account's bonus terms. Some say "90 days from completion," others say "90 days from your first deposit." Some require you to keep the account open for a full calendar year.
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Verify the bonus has actually hit. Don't close an old account until you've verified the bonus landed in your new account. Bonuses sometimes take 60–90 days to process. Call your bank if it's late.
Common Questions
Can I close my old account as soon as the seven-day CASS period is over?
No. CASS completes in seven working days, but that just means the switch is processed. You need to keep the old account open for at least 30 more days to ensure all direct debits have migrated, and for 90 days to protect your bonus.
What happens if a direct debit bounces on my closed old account?
You'll be charged an unpaid item fee (typically £5–£10) by your new bank, and the payment will fail. You'll need to manually pay the bill. The provider will be unhappy, potentially causing a missed payment mark on your credit file.
Do I pay tax on interest earned during the parallel run?
Yes. Any interest earned is taxable income for the tax year, regardless of how many accounts you're running. If you earn more than your Personal Savings Allowance (£1,000 for basic-rate taxpayers), you'll owe tax on the excess.
Should I move all my money to the new account immediately?
No. Keep a buffer in the old account (usually £500–£1,000) to cover any stragglers. Move the rest to the new account gradually over the first 30 days as you confirm direct debits are migrating successfully.
What if my bonus doesn't arrive within 30 days of the switch completing?
Contact your new bank. Some bonuses take 60–90 days, depending on the terms. Ask for a reference number and written confirmation of the expected arrival date. If it's genuinely late beyond the terms, escalate to the bank's complaints team.
Running accounts in parallel is tedious, but it's the only way to switch without losing money. February is when most people are doing this, and most people are doing it wrong. If you're in the middle of a switch right now, stop and set up a tracker. It'll take 10 minutes and save you hundreds in missed bonuses or unpaid item fees.