I don’t know one financial advisor or planning that doesn’t use some financial modeling program to build a financial plan. Unfortunately, these programs are very complex with default assumptions that need to be adjusted. Too often, the output is wrong, resulting in bad financial advice. 

I manually check every number in every year of my financial models, even taxes. With a pen and paper, I’ll calculate your state and federal taxes, as well as Social Security and Medicare taxes, and compare them against the model. It’s only when I’m confident about the numbers being locked down do we start exploring the possibilities.