Once you set the value for your home when you start using it for business, you do not make adjustments.
Please see the instructions for Form 8829:
Lines 37 Through 40
Enter on line 37 the cost or other basis of your home (including land), or, if less, the fair market value of your home on the date you first used the home for business. Do not adjust this amount for depreciation claimed or changes in fair market value after the year you first used your home for business.
An assessment on your house would not "change" anything on Form 8829.
Once you set the value for your home when you start using it for business, you do not make adjustments.
Please see the instructions for Form 8829:
Lines 37 Through 40
Enter on line 37 the cost or other basis of your home (including land), or, if less, the fair market value of your home on the date you first used the home for business. Do not adjust this amount for depreciation claimed or changes in fair market value after the year you first used your home for business.
@hmness5 wrote:The form uses the value of your house in the calculation
It uses the lower of (a) Cost or (b) Fair Market Value on the date it was FIRST converted to business. Any value changes after that date do not affect it.
[EDIT: Sorry, I didn't see Rachel's comment right above mine, so my post basically says the same thing.]