[EvanDotPro]

Around 2007-2008, as a "side project" I tried to build a web-based payroll software for a single state. Me and the developer I employed were able to get to 80% real quick, with ACH and everything. But as you say, the final 20% (edge cases) are nearly endless and ever-changing. Even a single state ended up being way too much for two developers.

[peteri]

Way back when I wrote accounting software in the UK. I had a conversation with my boss about us writing our own payroll software so we didn't have to a pay a third party to white label their software.

I then went and found out how many folks one of our competitors (a bit more mass market than us) had writing payroll software.

The answer was it was a six person team just to keep up with the government changes every year. We never bothered any more with that idea.

Payroll is surprisingly hard.

[mgkimsal]

I switched payroll providers a few years ago away from Quickbooks Payroll. They hosed up my stuff so bad I was dealing with the fallout for close to 2 years afterwards - overpaid, underpaid, refunds, fines, it was a mess.

The new company I switched to did not allow me to do payroll on the days that I'd wanted. They only offered 2 or 3 options, none of which matched what I'd done before. "That's all we offer" was the reply. There've been a couple other 'restrictions' (lost flexibility) on some behaviors - nothing horrible, of course.

I've no doubt removing some of that flexibility has reduced their overhead - there's enough changing regulations every year in multiple jurisdictions - keeping the main stuff under their control as simple as possible seems to have worked out for them. I've had... 4 years with them without incident, but 2 years of pain with QB before.

FWIW, QB hosed up dealing with my state. Federal was fine, but they created so many problems with my state filings...