And have you ever read the forms? I don’t know if writing the software could be seen as tax advice or filing on behalf of someone.

Who would use the software if it didn't suggest ways to save them money, which would then take on the burden of actually being legally correct? UK tax accounts can be submitted directly to the government which requires an additional level of checks by them. Accounting is relatively simple to understand for UK accounting... until it isn't. It becomes very complicated, very quickly, and that dramatically alters the database schema, alters workflows, and this stuff can be in a constant state of flux. Corporate accountancy laws are very different to personal tax accounting, and keeping abreast of both situations can be very difficult to manage.

I spoke to a person representing a fairly small commercial accounting SaaS who said they specifically only target high-net-worth companies who can afford to pay the prices they need to turn a profit, and that's why they put on silly fake award shows (my words) for people within these companies (mostly c-suite people) to placate them into spending more money with them.

Doesn't sound good now does it? No one will take that responsibility for free.