SG52500 | Giving security: security deposits: effect on VAT default surcharges
From HM Revenue & Customs · Securities Guidance
A security deposit is not a pre-payment of VAT, but it would be disproportionate to apply a surcharge where we hold a security deposit so it should be taken into account when calculating a surcharge.
You should inhibit automatic surcharge processing while a deposit is held by completing a VAT719.
Don’t forget to lift the inhibit when the security deposit is no longer held.