B2B ESS exemption

For a US-based seller of Software-as-a-Service (SaaS) to UK-based customers, are transactions completely exempt from VAT for all parties? I've read up on guidance pertaining to place of supply, reverse charges, and other matters, but I'm wondering if there is definitive guidance stating that these services are exempt. My understanding is that SaaS is considered an electronically supplied service (ESS) and, when sold B2B, is exempt.

An annoying part of the VAT legislation is that an "exemption" is not the same as saying a supply is "exempt". Not your fault, blame the legislators. Your supply will either be standard rated/UK VAT charged or else outside the scope of VAT. https://www.gov.uk/guidance/the-vat-rules-if-you-supply-digital-services-to-private-consumers In essence if your customer is B2B then your supply is outside the scope of VAT, no VAT is charged on your invoice and customer in UK accounts for VAT themselves under reverse charge rules. If customer is B2C, then you are required to register for UK VAT and charge UK VAT. When reading the above link/guidance, read it carefully and in full, not just bits of it. For example, the first section states "If you are a business making supplies of digital services to UK consumers, those supplies are liable to UK VAT", which is correct, but note it refers to a "consumer" which means B2C, you have to read much further down by stating "If you accept that your customer is in business, the supply does not come within the scope of these business-to-consumer arrangements. With a cross-border business-to-business supply the customer will be responsible for accounting for any VAT due to the tax authorities in their country."

Thank you so much for your very helpful response. Am I correct in interpreting that SaaS falls outside the scope of reverse charge rules (VAT Notice 735.3.1)? https://www.gov.uk/guidance/the-vat-domestic-reverse-charge-procedure-notice-735#which-specified-goods-and-services-the-reverse-charge-applies-to

Hi Jonathan Mann,
If you are selling such services these would be Outside The Scope of UK VAT and would be accountable by your business customer under the reverse charge procedure
Please see the guidance below:
The place of supply rules for services
Use and enjoyment
Thank you.