Real estate purchase in community of accrued gains

Hello,

I would be very grateful for any hints and assessments regarding the following case:
Ms. F and Mr. M are married under the community of accrued gains regime and are buying a property. Ms. F insists on emotional grounds that the property be acquired with ownership shares of 50% each.

Premarital assets: M has €600k, F has €200k, total assets are €800k. For simplicity, there is no accrued gain.

The property costs €800k and is paid from the assets, and registered in the land register with ownership shares of 50% each.

In the event of a divorce, M and F would each have assets of €400k, resulting in the following accrued gains:
M: -€200k -> set to zero, since there is no "negative accrued gain"
F: +€200k
Accrued gains equalization: F must pay €100k to M.

Assets after equalization:
M: €500k (i.e., a loss of €100k)
F: €300k (a gain of €100k)

If the property had been acquired with a 75% ownership share by M and 25% by F, this shift would not occur. However, F insists on owning 50% of the property – what rules or options do you suggest to balance this inequality? Ideally without a notarized marriage contract.

What occurs to me spontaneously:

[*] M always ensures that future accrued gains are held in an account/depot in his name. Only this way can he avoid the disadvantageous negative accrued gain.
[*] M and F conclude a loan agreement (interest-free and without repayment terms?) for the €200k that F "gains" in assets through the property purchase. What formal requirements exist for this loan agreement so that it effectively acts as an "IOU" from F to M in the accrued gains equalization?
[*] Notarized marriage contract that, deviating from the statutory regulation, requires negative accrued gains to also be compensated? But this carries risks if one spouse gets heavily into debt.
[*] What else do you think of?

I would be very grateful for hints and advice!

In the event of a divorce, M and F would each have assets of €400k, resulting in the following gains

No, there is a joint asset of €800,000, from which the initial assets are deducted and the gain is halved.

No, there is a communal property of €800,000, from which the initial assets are deducted and the accrued gain is halved.

Unfortunately, this does not correspond to the legal situation; negative gains on one side are definitely not compensated. Otherwise, I would not have asked the question, and the case would have been conclusively settled with a 50% entry.

No, there is a joint property of €800,000, from which the initial assets are deducted and the increase in value is halved.

I don't understand that. How is that supposed to work? What is supposed to be deducted from what? Besides, there is no joint property. The house belongs half to each partner.

For me, there are only two possibilities. 1. The property is not purchased. Then the emotional woman just has bad luck. 2. Notarial marriage contract.

negative gains on one side are definitely not compensated.

Who says that? See 1375 Building Code.

Unfortunately, this does not correspond to the legal situation; negative gains on one side are definitely not compensated.

Otherwise, I would not have asked the question, and the case would have been conclusively settled with a 50% entry.

there is no negative gain here!

they have 1) 800k in assets, divided into M=600k, F=200k
2) buy a property for 800k, 50/50 is the share of the property, but since it was acquired from equity BEFORE the marriage, it does F no good that she holds 50% of it!

in case of a divorce:
property is sold for 800k = 0.00 gain/loss = no gain! = M gets 600k refunded, F gets 200k refunded
property is sold for 600k = 200k loss since it belongs 50/50, M will get 500k, F only 100k then
property is sold for 1000k, = 200k gain, so each makes 100k profit (thanks to gain!) thus M gets 700k, F 300k

of course, it is optimal to make a contract where the premarital equity is exactly itemized.
This would secure both sides.
See above (200k loss, then each bears 50%; 200k gain = each bears it 50% into their own pocket).

PS. in community of accrued gains, only the assets accumulated during the marriage are considered 50/50. Those from before the marriage are accordingly deducted again.

PS2. if F does not agree to this modified contract, then do the following:
M pays 200k, F pays 200k, the 400k is "externally financed" where the house and both spouses are debtors!
M keeps the higher share of 400k!
(if something goes wrong here and M pays the 400k to the bank, he can later recover the corresponding share upon sale)