How do I keep track of realized capital gains when selling taxable investments?

[Morning Glory]

This question might sound stupid, but seriously I find out when I get my statements at tax time and it's not usually that much.
Planning to FIRE this December at ~ 1 million net worth, split pretty evenly between taxable and traditional. (We are not averse to part-time work if the market fails or we want to move to a more expensive area for kids' needs, just need a break right now). If I want to do Roth conversions and stay under the cutoff for ACA subsidies and CSRs, I need to know the total of my other income  by December ,well before the statement comes out. (even so, I would allow some room in case dividends hit on 12/31).

It looks like the best subsidies happen if I keep my taxable income below 45k (family of four, adults would be on silver ACA with zero premium and low deductible/due to CSRs, kids would be on CHIPs). We spend about 40k per year (this will hopefully be less without the medical premiums and copays for the kids). The states we are looking at moving to don't have expanded Medicaid.  So say if 20K of our taxable withdrawal is dividends and gains, we can do a Roth conversion of 25K at the end of the year.

-Problem is we have a lot of small accounts that I want to use in the first year or two in order to simplify things (what Collins calls cats and dogs). I followed Collins' advice and just left them alone with a plan of using them first after retirement (for example I have 22k worth of individual stocks in Robinhood. Most of them got transferred a long time ago from Scottrade , well before I discovered this forum, and the cost basis that shows up in the app is incorrect [the correct amount is under the hood somewhere, because if I sell something it shows up at tax time]). Husband has a similar account with about 35k, and he wants to keep it and continue trading stocks in small amounts, which gives me a headache at tax time already. Don't even get me started on the crypto, he's promised to get rid of that before the end of the year so I only have to fill out that form one more time.

-another option would be to sell the stocks this year while I'm still on employer insurance. I have room in the 0% capital gains bracket but I would possibly lose out on the $400 saver's credit. Again I would have to add up everything I've made working, from dividends, interest, gains, etc., before I did this.
ETA my state treats capital gains the same as earned income so I would pay ~7% in state income tax if I chose this option

I use Mint to keep track of my transactions on credit cards and stuff, but it's not very accurate. Would Personal Capital be a more reliable tool to track this? 

TLDR: I don't want to screw something up and think I only had 20k of gains when it's really 30k, then Roth convert too much and have my income too high for subsidies.

[MDM]

...the cost basis that shows up in the app is incorrect [the correct amount is under the hood somewhere, because if I sell something it shows up at tax time]).

That's the heart of the issue.

Probably worth calling the brokerage and asking someone to walk you through identifying your cost basis.

If you plan to sell all lots of a particular stock/fund, all you need is the total basis for that stock/fund.

If you plan to sell only some lots of a particular stock/fund, you should identify the basis for each lot and ensure your cost basis method is "specific ID" (or whatever name your brokerage gives to the ability to choose which lots to sell).

[Morning Glory]

...the cost basis that shows up in the app is incorrect [the correct amount is under the hood somewhere, because if I sell something it shows up at tax time]).

That's the heart of the issue.

Probably worth calling the brokerage and asking someone to walk you through identifying your cost basis.

If you plan to sell all lots of a particular stock/fund, all you need is the total basis for that stock/fund.

If you plan to sell only some lots of a particular stock/fund, you should identify the basis for each lot and ensure your cost basis method is "specific ID" (or whatever name your brokerage gives to the ability to choose which lots to sell).

Thank you. Calling them is good advice!!

I think I'll do the "all lots" method, since my largest holding is $5400 (I've had that one since 2009 and it's pretty much all gains), and most of them are < 1000. 

These little accounts are heavier on gains than my big account at Vanguard, just because I've had them longer. I have the luxury of way more than 5 years worth of taxable accounts though, so if I did a tiny Roth conversion the first year it wouldn't be a big deal.

I'm thinking of doing withdrawals quarterly, although ERN, Mad Fientist, et al say the frequency doesn't really matter.
 

[MDM]

...I've had that one since 2009....

The onus is on you to know the cost basis for shares purchased that long ago.  Those are known as “noncovered” securities - see that link for more.

The brokerage might have that number for you.

When you file your tax return, you check different boxes for "covered" vs. "noncovered" share sales, but the math doesn't change: the cost basis is subtracted from the sale proceeds to get the taxable amount.

[secondcor521]

MDM is, of course, spot on with regards to investment basis.

I wanted to comment on some other things:

1.  The saver's credit for MFJ drops from a 20% credit to a 10% credit at $43,001 of AGI.  So you'd maybe drop from a $400 credit to a $200 credit.  One trick you can do is figure your taxes in January next year when you have all the numbers, then make a deductible traditional IRA and/or an HSA contribution to lower your AGI to $42,999.  You'll get a deduction for the IRA/HSA contribution and get the higher saver's credit.

2.  For 2021 and 2022, the ACA subsidy cliff has been eliminated due to the American Rescue Plan Act.  So if you Roth convert too much, your subsidies will probably be lower but they probably won't go away.  I like to think of the loss of subsidies as about a 10% to 15% additional tax on income.  In your situation, however, this probably won't even matter, because 400% of FPL (where the cliff used to be) for a family of 4 in the lower 48 for 2022 is about $106K.  Your AGI sounds like it will be much lower.

Your brokerage firm where you hold these small holdings may have a web page showing YTD tax information.  Vanguard does.  So if you sell early enough, you can just look there.

Also, two minor points that you're probably aware of:  1.  Roth conversions, to count for 2021, need to be done in the calendar year, so deadline is 12/31/2021, and 2.  Roth conversions can no longer be undone, so be 100% sure you want to convert before clicking that final confirmation button.

[Morning Glory]

Thanks. That sounds like an mpp: I was so good at leaving my shit alone that now it's a pain to sell it so it's tempting to just leave it alone some more.

 One question: my AGI last year was ~57k and we got a $400 credit, so it must be $200 each for myself and spouse???

Another question: on the healthcare.gov site the deductibles and copays are quite a bit higher if I set the income over 45k. What happens with those at the end of the year if I guess my income too low?

I don't mind paying taxes. The medical copays/coinsurance bother me more because they add up to a big chunk of my spend and can be unpredictable. It feels like a penalty for being sick/disabled/whatever, or for actually getting help for mental health issues. On my employer plan there is a $40 copay for each visit that doesn't count towards the oop max (we've met that already this year too).

We're currently in the application process to get secondary medicaid for the youngest kid because he needs behavior therapy for autism. I don't know if every state has this option available but I can obviate the need by having the kids on chips. I think that phases out around 250% fpl in the states I'm looking at moving to, and it is required by law to cover that therapy.

  I probably won't start Roth conversions until December 2022. I've already made deductible tira contributions for 2021, for myself and spouse. No HSA (I would have been worse off with an hdhp).

I just got access to a 457b this year but didn't start contributing until after I sold my house in June, trying to max it out before the year ends, so my income for 2021 should be pretty low (Im also contributing to my 401a, and I put some in a 403b at my old job in January).

[terran]

Good comments so far. One thing I'd add is that dividends are usually announced for most funds by mid December, or Christmas at the latest, so there are a few days in which you can calculate your exact income and still have time to make Roth conversions (assuming you can figure out the capital gains issue that is).

[terran]

One question: my AGI last year was ~57k and we got a $400 credit, so it must be $200 each for myself and spouse???

At that income level it's 10% of your retirement plan contributions on up to $2000/person of contributions, so as long as you each contribute at least $2000 to a retirement plan and meet the other conditions then yes, it's $200 for each you and your spouse.

[secondcor521]

[1] One question: my AGI last year was ~57k and we got a $400 credit, so it must be $200 each for myself and spouse???

[2] Another question: on the healthcare.gov site the deductibles and copays are quite a bit higher if I set the income over 45k. What happens with those at the end of the year if I guess my income too low?

[3] We're currently in the application process to get secondary medicaid for the youngest kid because he needs behavior therapy for autism. I don't know if every state has this option available but I can obviate the need by having the kids on chips. I think that phases out around 250% fpl in the states I'm looking at moving to, and it is required by law to cover that therapy.

[Some stuff removed, numbers added for reference.]

1.  See terran's comments.  If you manage to get your 2021 AGI down to $42,999 and both contribute $2K to retirement plans, then your credit would be at the 20% level, so it'd be an $800 credit.  Nice if you can get it, but given the rest of what you posted, may or may not be possible.  Just a breakpoint in the tax code to be aware of.  (And the $43K breakpoint goes up a bit each year.)

2.  Deductibles and copays are set based on your estimated AGI.  Subsidies are based on your estimated AGI.  Subsidies are reconciled at tax time based on the relationship between actual AGI and estimated AGI.  Deductibles and copays are *not* reconciled at tax time.  (What you might be seeing is CSRs, which are *not* reconciled at tax time, are only applicable to Silver plans, are usually implemented by reductions in deductibles and copays, and most notably increase as your AGI drops below 200% FPL, which in your case is probably 200% * $26,200 = $52,400.)

3.  The CHIP AGI limit may vary by state.  In my state it is 185% of FPL IIRC.  It's possible for parents to be on ACA and kids to be on CHIP, as you mention in your OP.