From a PM discussion Cheddar Stacker and I had for his tax guide post
Some suggestions that have been made in various posts for tax planning "what-if?"s: https://irs.gov/Individuals/IRS-Withholding-Calculator
the MMM case study spreadsheet
Looking closer at all four:
- The IRS withholding calculator isn't bad, but requires you to know how much you will get in credits.
- bankrate appears to calculate the child tax credit and the non-refundable American Opportunity credit, but relies on user input of the credit amount for for all others (and is still using 2014 tables)
- taxcaster has significant holes for the usual MMM audience: taxcaster does not calculate the saver's credit, and may not handle passive income (from rentals) well.
- The spreadsheet does the saver's, child tax, child/dependent care, the American Opportunity education, and earned income credits.
One also has the options of
- using the previous year's full blown version of TaxAct, TurboTax, etc. Both TaxAct and TurboTax have "what if...?" capability for future tax years. E.g., see https://bogleheads.org/forum/viewtopic.php?f=2&t=225670#p3492987
- developing a personalized tax spreadsheet that covers one's own situation very well, even if it would not apply well to others. E.g., see /ask-a-mustachian/turbo-tax-vs-cpa/msg539186/#msg539186
ETA: spreadsheet now does tax calculations for SS recipients
ETA2: replace paycheckcity with the IRS calculator
ETA3: The case study spreadsheet does calculate the child/dependent care credit and the American Opportunity education credit.
ETA4: Note TaxAct's and TurboTax's "what if?" capability for future years.