how do taxes interact?

[mistymoney]

so say you make 100k. fica is 7650. Does federal income tax go on 100k or 100-7.65k?

then does state tax go where? after fica and fed are removed?

[MDM]

FICA tax does not affect federal or state income tax.

Various pre-tax amounts (HSA, 401k, employer-provided health insurance, etc.) can affect both federal and state income tax.

State tax goes on the state tax return.  Only if you itemize on the federal return might your state tax affect your federal tax.

Might be worth going line by line through your most recent https://www.irs.gov/pub/irs-pdf/f1040.pdf and analogous state return so you understand why each line/box has the value it does.

The Case Study Spreadsheet will display the formulas used for each cell, so you might compare those with the official form instructions.  Some comparisons will be straightforward, while some - due to this being Excel and trying to accommodate various situations, with all that entails - may be harder to decipher in the spreadsheet than in the IRS instructions.

It would be interesting to hear how it goes if you do try the line-by-line analysis of your most recent return.

[terran]

FICA tax does not affect federal or state income tax.

Except when it's self employment tax, in which case you get a deduction for the "employer" half.

[MDM]

FICA tax does not affect federal or state income tax.

Except when it's self employment tax, in which case you get a deduction for the "employer" half.

Yes, and you pay both the employee and employer shares with your federal tax return. 

The question in the OP implied a W-2 income, for which the employer remits both portions to the IRS and the employees never see their share (except as a printed number on their pay stubs).

[mistymoney]

FICA tax does not affect federal or state income tax.

Various pre-tax amounts (HSA, 401k, employer-provided health insurance, etc.) can affect both federal and state income tax.

State tax goes on the state tax return.  Only if you itemize on the federal return might your state tax affect your federal tax.

Might be worth going line by line through your most recent https://www.irs.gov/pub/irs-pdf/f1040.pdf and analogous state return so you understand why each line/box has the value it does.

The Case Study Spreadsheet will display the formulas used for each cell, so you might compare those with the official form instructions.  Some comparisons will be straightforward, while some - due to this being Excel and trying to accommodate various situations, with all that entails - may be harder to decipher in the spreadsheet than in the IRS instructions.

It would be interesting to hear how it goes if you do try the line-by-line analysis of your most recent return.

Thanks, I ha d found some info online before posting, but I thought - they can't actually be charging income taxes on the fica money! well - I was wrong!

State tax is interesting that it varies. I do itemize. I have an EA that does my taxes because they are a little complicated and I feel better with a professional filing them. And since I went to him, he has sved me much more than his fees!

[mistymoney]

FICA tax does not affect federal or state income tax.

Except when it's self employment tax, in which case you get a deduction for the "employer" half.

Thanks for this! I had not put into OP but I do have side gig income that I plan to keep going for several years after quitting the day job, and part of this post was trying to figure out how much in taxes I would need to pay on that side income as I estimate my withdrawals and WR. So appreciate this clarification.

Much more an issue of me understanding how it all will work together for accurate estimates, rather than doing the taxes as I mentioned I have an EA and will stick with them for at least a few years after retirement. At some point I think the taxes might become simpler and I could take over if need be. But right now and for the immediate future, I like the peace of mind.

[MDM]

State tax is interesting that it varies. I do itemize. I have an EA that does my taxes because they are a little complicated and I feel better with a professional filing them. And since I went to him, he has sved me much more than his fees!

A significant value for understanding taxes can be the things you do during the tax year because you understand how they will affect your return when you file next year.  E.g., whether to make traditional or Roth contributions based on your Marginal tax rate, etc.

Are you at that point yet?

[mistymoney]

State tax is interesting that it varies. I do itemize. I have an EA that does my taxes because they are a little complicated and I feel better with a professional filing them. And since I went to him, he has sved me much more than his fees!

A significant value for understanding taxes can be the things you do during the tax year because you understand how they will affect your return when you file next year.  E.g., whether to make traditional or Roth contributions based on your Marginal tax rate, etc.

Are you at that point yet?

I am starting roth convertions that I will do for a few years. I am fine doing them into the 24% tax rate, but I definitely want to stay out of 32%

Plan to be a little flexible depending on how the market and tax rates pan out over time. Still working out this strategy.

[MDM]

I am starting roth convertions that I will do for a few years. I am fine doing them into the 24% tax rate, but I definitely want to stay out of 32%

Plan to be a little flexible depending on how the market and tax rates pan out over time. Still working out this strategy.

Depending on your age and health insurance, either of Roth Conversion and Capital Gains On ACA Health Insurance or Roth Conversion with Social Security and Medicare IRMAA might be worth a read.

[mistymoney]

I am starting roth convertions that I will do for a few years. I am fine doing them into the 24% tax rate, but I definitely want to stay out of 32%

Plan to be a little flexible depending on how the market and tax rates pan out over time. Still working out this strategy.

Depending on your age and health insurance, either of Roth Conversion and Capital Gains On ACA Health Insurance or Roth Conversion with Social Security and Medicare IRMAA might be worth a read.

thanks! will read it up!