I don't think so, Ive never seen it, I always do it manually for ACA clients

MAGI isn't a set thing.  You mentioned there are many uses or reasons for MAGI, but each of those uses/reasons may calculate MAGI differently for that specific purpose.  There are about a dozen different forms of MAGI, depending on what the MAGI is being used for. 

You would need to clarify which MAGI you are looking for.

I think there is only one MAGI and it's defined in Publication 17. Why would there be different ones?

How do you calculate it for ACA clients?

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@jgm6520 wrote:

How do you calculate it for ACA clients?

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ACA includes 100% of SS income in the MAGI, there might be a few other additions/omissions, but that seems to be the most common one.   Im sure healthcare.gov has an MAGI FAQ section.

Anything with a modified AGI will have a worksheet in the instructions detailing the calculations.

By ACA I assume you mean PTC.  That one's on page 8 of the instructions:

https://www.irs.gov/pub/irs-pdf/i8962.pdf#page=8

But NIIT was also born out of the Affordable Care Act.  It has a different MAGI calculation (just to use as an example that they are not all the same):

https://www.irs.gov/pub/irs-pdf/i8960.pdf#page=20

In general, the various MAGI calculations help to apply ordering rules to various tax breaks granted by Congress so as to avoid circular calculations.  Ironically PTC/SEHI is the exception to the rule and involves a circular calculation.

The program calculates MAGI on Form 8962.

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@jgm6520 wrote:

The program calculates MAGI on Form 8962.

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why are you asking how to calculate it if the program does it for you?

Youre not limited to one line comments,  you can give all the information at once....what are you really asking?

@jgm6520   Google is your friend:

https://www.healthinsurance.org/glossary/modified-adjusted-gross-income-magi/