The Flexible Space Association said operators are failing to to challenge incorrect tax bills for fear of being landed with even more onerous rates liability for their whole building.
Average managed office desk rates were £230 above their serviced counterparts in Q4, but serviced space demand remained strong as operators cut prices.
The sale of 90 Whitfield Street in Fitzrovia comes as the London office developer plans to ramp up its disposals, which totalled £616.1m last year.
In response to feedback received during consultation, the developer will reduce the height and massing of its 1 Silk Street scheme, as well as enhance the design and privacy measures.
The group increased its profit after tax from £398.4m in 2024 to £531.4m in 2025, as its number of clients topped one million.
The 11-storey building, opposite Hammersmith Broadway, spans 105,237 sq ft, of which 63,250 sq ft is currently let.
The firm's portfolio value fell by 2.9% in H2 2025, ending the year at £555.2m.
Strong rental yields and affordability propelled the Scottish city to first place.
Law firm BCLP, which obtained the data from the Valuation Office Agency, said the surge in cases point to a system "under significant pressure" and could affect investment decisions.
Quantexa has agreed a 10-year lease at The Delft, which is scheduled for completion in spring 2027.
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