Maximising the June 2026 Marriott to United 25% Transfer Bonus

British Airways pushed its Avios cash fees up again on 27 May 2026. If you are feeling fee fatigue, you are not alone. UK flyers need low-tax alternatives for premium cabins. Because American Express UK does not partner directly with United Airlines, routing your Membership Rewards through Marriott Bonvoy during the June 2026 25% transfer bonus creates a phenomenal backdoor into Star Alliance flights with zero fuel surcharges.

Why the May 2026 British Airways fee hike changes everything

The UK points landscape shifted heavily late last month. When British Airways implemented its new, higher cash requirements for Avios reward flights on 27 May 2026, it fundamentally changed the maths for UK-based collectors. We are now seeing long-haul business class redemptions demanding eye-watering cash co-payments alongside the Avios.

Readers of Points Uncovered have been asking for alternatives. Many of you are sitting on massive Amex balances right now. The spring 2026 90,000-point “Invite a Friend” offers and the 100,000-point Platinum retention bonuses left UK accounts flush. But pouring those points into British Airways Executive Club feels significantly less rewarding today than it did in April.

You want high-value, low-tax redemptions. The United MileagePlus programme delivers exactly that. United does not pass on the dreaded carrier-imposed surcharges that European airlines love to invent. The problem? You cannot move Amex UK points directly to United. You have to get creative.

The maths behind the Amex to United backdoor

You can currently convert American Express UK Membership Rewards into United MileagePlus miles at a highly lucrative 1 to 0.93 ratio. This requires moving points through Marriott Bonvoy to stack two separate bonuses.

Here is exactly how the numbers break down right now:

• Amex UK points transfer to Marriott Bonvoy at a 2:3 ratio. This means 40,000 Amex points become 60,000 Marriott points.
• Marriott Bonvoy points transfer to United MileagePlus at a baseline 3:1 ratio.
• Thanks to the ongoing RewardsPlus partnership between Marriott and United, you get an exclusive 10,000-mile bonus for every 60,000 Marriott points you transfer. Therefore, 60,000 Marriott points become 30,000 United miles.
• Throughout June 2026, United is running a 25% bonus on hotel transfers. This adds another 7,500 miles to your transaction.

When you stack it all together, 40,000 Amex points yield 37,500 United miles. You are effectively getting a 93.75% transfer rate into a top-tier Star Alliance frequent flyer programme. Given that Amex UK usually makes it incredibly difficult to access Star Alliance without losing massive value, this is a phenomenal return.

Zero fuel surcharges on Star Alliance flights

United MileagePlus completely blocks carrier-imposed surcharges on all award tickets. This is the main reason you should care about acquiring United miles in 2026.

If you use Avios to book a British Airways flight to Tokyo, you will pay hundreds of pounds in taxes and fees. If you use United miles to book an ANA flight to Tokyo, you pay the genuine government taxes. That is usually under £50. The same rule applies to Lufthansa, SWISS, TAP Air Portugal, and Air Canada. United simply refuses to pass those junk fees onto you.

Here is the thing. Finding Star Alliance premium cabin availability out of London Heathrow is entirely possible if you are flexible. SWISS business class via Zurich or Lufthansa via Frankfurt opens up massive global routing options. By using United miles, you bypass the heavy cash penalties these airlines normally charge their own frequent flyers.

How to execute the June 2026 transfer bonus

You must input your MileagePlus number and register on the dedicated United promotional page before initiating the transfer from Marriott. If you skip this step, the 25% bonus will not trigger, and United customer service will not fix it for you retroactively.

Step 1: Register with United

Log into your United MileagePlus account and find the June 2026 hotel transfer promo page. Enter your details and click register. Take a screenshot of the confirmation screen. You probably will not need it, but I always prefer having proof.

Step 2: Move points from Amex to Marriott

Log into your American Express UK account and transfer your Membership Rewards to your linked Marriott Bonvoy account. In my experience, this transfer is usually instant. Refresh your Marriott app, and the points should be sitting there.

Step 3: Move points from Marriott to United

Log into Marriott Bonvoy and navigate to the point transfer page. Select United MileagePlus. Transfer in exact blocks of 60,000 Marriott points. If you transfer 50,000 points, you miss the 10,000-mile RewardsPlus bonus. If you transfer 70,000 points, 10,000 of those points are moving at a miserable 3:1 ratio with no Marriott bonus. Stick to multiples of 60,000.

Step 4: Wait for the miles to arrive

This is genuinely the most annoying part of the process. Marriott to United transfers are not instant. As of June 2026, they typically take 48 to 72 hours to land in your MileagePlus account. The base miles usually show up first, followed by the 25% promo bonus a day or two later.

Hitting the 25,000-mile promo cap

The June 2026 United 25% bonus is capped at 25,000 bonus miles per MileagePlus account. To max this out, you would need to transfer enough hotel points to generate 100,000 base miles.

If you want to push this promotion to its absolute limit, here is the exact maths:

You need to transfer 400,000 Marriott points. This yields 133,333 base miles, plus the Marriott RewardsPlus bonus of 60,000 miles (since you transferred six blocks of 60,000, leaving 40k extra — actually, to optimise perfectly, you should transfer 360,000 Marriott points or 420,000 Marriott points).

Let’s look at a perfectly optimised maximum transfer of 420,000 Marriott points. This yields 140,000 base miles plus 70,000 Marriott bonus miles, totalling 210,000 miles before the United promo. The 25% promo applies to the base and Marriott bonus. 25% of 210,000 is 52,500. Since the cap is 25,000, you are wasting potential bonus miles by going this high.

The true optimal ceiling for this specific promotion is transferring 300,000 Marriott points. Here is why:

• 300,000 Marriott points = 100,000 base United miles.
• Five blocks of 60,000 trigger five 10,000-mile Marriott bonuses = 50,000 bonus miles.
• Total before United promo = 150,000 United miles.
• 25% United promo on 150,000 = 37,500 miles. You hit the hard cap of 25,000 miles.

To fund that 300,000 Marriott point transfer, you need 200,000 Amex UK points. That yields a total of 175,000 United miles. Still an excellent return.

Practical alternatives for Star Alliance

Singapore Airlines KrisFlyer is the only direct Star Alliance transfer partner for Amex UK, but the conversion rate is poor. Amex points transfer to KrisFlyer at a 3:2 ratio. You lose a third of your points immediately.

Worse, while Singapore Airlines does not charge fuel surcharges on its own flights, it does pass them on when you book partner airlines like Lufthansa. If you use KrisFlyer miles to fly Lufthansa business class, you will pay the heavy cash fees. This makes the United backdoor significantly more attractive for UK flyers looking to travel westward to the US or short-haul into Europe.

My honest verdict on this promotion

Honestly, I am entirely convinced the maths works for anyone holding a large Amex balance right now. Generating Star Alliance miles at a 1 : 0.93 ratio from a UK credit card is exceptionally rare.

The part I keep coming back to is the 72-hour transfer delay. Award availability changes by the hour. If you spot a rare ANA First Class seat, transferring points and waiting three days means you will almost certainly lose that seat. This strategy requires patience and flexibility.

However, United MileagePlus miles do not expire. If you have 80,000 Amex points doing nothing, speculatively moving them into United right now locks in the 25% bonus. You can then book a zero-surcharge Star Alliance flight anytime in 2027 when a seat drops. With British Airways squeezing Avios collectors for every spare pound, having a stash of United miles is the smartest hedge a UK flyer can make this summer.

Ready to optimise your next redemption? explore more guides on Points Uncovered.