Can I still claim a total of five allowances on line 5 even if my totals for A-H is only 2?
Yes.
Your responsibility is to have the correct (within the safe harbor rules) amount withheld. You may use whatever W-4 entries needed to do so.
You could also check withholding calculations in the case study spreadsheet. If that also suggests 5 allowances, there is an even better chance you have the correct number.
Thanks for the spreadsheet. Interestingly, the spreadsheet suggests 3 allowances to break about even ($160 refund) vs. the W4 Turbo calculator suggesting 5 allowances to receive a $165 refund. Has anyone done a comparison between these two calculators for their situation? I'm thinking I should play it safe and use 3. Worse case scenario I'll receive a little bit more of a refund.
How do the two parts (1. Tax due; 2. Amount withheld) compare in each tool?
The TurboTax W4 calculator doesn't break down the numbers. It just spits out the estimated refund and a slider to adjust the allowances (see attached image). The other tool TaxCaster does show me tax due/withheld but only for 2017 at the moment. It does give me the same estimated 2018 tax refund amount as the W4 calculator.
Spreadsheet tax due = 3038 ; withheld = 4196
With my current '1' allowances, here is the refund differences from the tools: $2315 vs $1158
