121 exclusion, 2 primary residence were sold within 1 year

TP sold first house and used 121 exclusion. 10 months later, TP sold another house which generated much more gain than the first one. He also met 2/5 year use and ownership rule at the time of the second sale. The first sale was in 2021 and didn't make full use of the 121 while the second sale was in 2022 and can make full use of the 121 exclusion.
Now he is considering amend the 2021 return so that he can remove the 121 exclusion from the first sale so that he can use the exclusion for second sale.
Is he allowed to choose which sale to use the exclusion?
Or, can he get partial exclusion for the second sale if it falls under change of job, health situations etc.?
Thanks

I'm curious to read other responses, but my intuitive thoughts are that:

1) Yes, you can amend the tax return to elect NOT claim the exclusion and the claim it on the 2nd sale, if it qualifies.

2) No, the "exceptions" seem to apply to the eligibility tests and not the limitation on how often you can take it (Publication 523 Eligibility Step 5). (EDITED: Incorrect given HowardS' post)

But how does the taxpayer(s) qualify for the 2nd (without an exception to the eligibility test) if they qualify for the first? How could he have lived in the most recently sold home for 2 years and have claimed the exclusion on another home?

I think you will need an exception to the eligibility test to claim it on the 2nd sale in addition to amending the prior tax return to remove the exclusion (and pay the tax and late fees).

I think you can make the election to not have the section apply on an amended return.
Treas. Reg. 1.121-4(g) simply says it is made by "filing a return" including the gain on the return within the 3-year period allowed for such return.

So you should be able to amend it to include the gain, and then use the exclusion on the second sale instead.

I'm curious to read other responses, but my intuitive thoughts are that:

1) Yes, you can amend the tax return to NOT claim the exclusion and the claim it on the 2nd sale, if it qualifies.

2) No, the "exceptions" seem to apply to the eligibility tests and not the limitation on how often you can take it.

But how does the taxpayer(s) qualify for the 2nd (without an exception to the eligibility test) if they qualify for the first? How could he have lived in the most recently sold home for 2 years and have claimed the exclusion on another home. I think you will need an exception to the eligibility test to claim it on the 2nd sale in addition to amending the prior tax return to remove the exclusion (and pay the tax and late fees).

I would think if the 1st qualified, then there will be some "non qualified use period" involved on the second sale. It is also possible the TP bought and moved from the first house to this house 2 years ago and therefore could meet the 2/5 period for both at the same time with no periods of nonqualified use.

Partial exclusion is available.
https://www.law.cornell.edu/cfr/text/26/1.121-3

(a) In general. In lieu of the limitation under section 121(b) and § 1.121-2, a reduced maximum exclusion limitation may be available for a taxpayer who sells or exchanges property used as the taxpayer's principal residence but fails to satisfy the ownership and use requirements described in § 1.121-1(a) and (c) or the 2-year limitation described in § 1.121-2(b).

Amazing.

I gotta get my head/research out of the pubs and into the law.

Thank you everyone for the help!

To calculate partial exclusion due to change of job, if the sale is due to one spouse changed job, the partial exclusion will include both spouses' portion of the exclusion right?
e.g. gain=400k
days from the first sale which uses 121 exclusion is 300 days
the partial exclusion=300/730 x 500k not 300/730 x 250k, right?
Thanks.

300/730 x 500k