Hi John Ray Patajo,
Even if you set the financial dimension as fixed value in Main account level, it will not be selected automatically in the budget register entry line when you select that main account where you have defaulted this dimension. But yes; in other type of journals, it will be selected as you already mentioned in previous comments. This is as per default design in D365.
Have you tried by setting the advanced rule structure and then add that advanced rule in configure account structure form?
Even though this setup will also not select the dimension in budget register entries automatically when you select that main account liked with it; however system will show you notification that 'Blank is not allowed for the combination' so that atleast you can be sure to select the respective dimension value for that dimension in budget register entry form.
Below are the steps I have checked.
--- I have a financial dimension LOB where the dimension value is AV.
--- Created an advanced rule structure with this value in accordance with main account combination of 522110.

--- Add this advanced rule structure with account structure P/L and activated the account structure.

--- Now created a budget register entry with this main account without selecting any dimension. System is showing this notification.

--- Also; if I now select the dimension LOB, it will by default show me only that value (AV) which is linked in advanced rule structure.

Let us know if alternatively you can use this feature to validate financial dimension in combination with main accounts in budget register entries form.
Best regards,
Sourav Dam
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