If you're legally required do your payroll with a buggy computer system rather than manually (and not even "this specific buggy computer that we gave you", just any old buggy piece of crap), then, uh, I don't really know what to say to that. My condolences, I guess?
If you mean it's impractical and error-prone to do payroll manually, well that's the point of automating >99.999% of it. For the remaining <0.001%, someone is going to have decide how to deal with it, and I'm sceptical that a programmer seven years ago will know better than a lawyer today what the legal requirements today are.
The level of aggressive ignorance in HN comments can be quite shocking. There is no legal requirement to use any particular payroll system. The payroll rules are written by domain experts including lawyers and others, and encoded into rules engines.
If you mean it's impractical and error-prone to do payroll manually, well that's the point of automating >99.999% of it. For the remaining <0.001%, someone is going to have decide how to deal with it, and I'm sceptical that a programmer seven years ago will know better than a lawyer today what the legal requirements today are.