I want attribute tax calculations

Products price have Net and Gross options. But attributes are not. I want calculate attribute price with tax.

Attribute tax is seriously problem for me. Someone help?

What do your products have for "Tax Class:"??
Have you setup a tax definition?

If this is set up then attributes will also have tax calculated into their price

But in entry on the admin will still only display the price as entered without having the combined "gross" and "net" values. If understand correctly the desire is to have both values displayed upon entry and/or as listed in the attributes controller when the attribute is affected by or included with other taxes.

I thought I saw a modified attributes controller as a "plugin" though I don't know if this factor is addressed in it. Otherwise some javascript similar to other areas of the admin could be used to accomplish the goal I explained above.

Tax Classes id 1. I have only one.
Admin> Catalog> Product Types ... Product Price Tax Class Default.. 1

And My store

Products are have Tax Class, and calculate tax products and attribute.
But when attribute price 1€, calculate and show 1.14€ (tax14%).
My store, Display Prices with Tax: true. And must be like this.

Admin> Catalog> Product Types ... Product Price Tax Class Default.. 1
This is not the tax zone I was talking about see this FAQ

https://www.zen-cart.com/content.php?118-how-do-i-configure-the-taxes-%28us-state-sales-tax-single-rate%29

I have done it already. Tax is working both of them, products and attributes.
My problem is, I just wanna add gross price to attribute tax, when 'My store.. Display Prices with Tax: true'. But It does not work in a correct way.

I just wanna add gross price to attribute tax
I do not understand the above comment???

I have a demo install HERE
Where the base price is $10 but is taxable and the attribute price is $5.00 and also tax is added
Is that not what you are seeing on your cart??

Can you try when My store.. Display Prices with Tax: true.

That setting checks for multiple tax rates
Do you have more than one tax rate setup?

If multiple tax rates apply, show each rate as a separate line at checkout

I have only one tax rate.
But if I do not choose 'Display Prices with Tax' its doesn't show price with tax. Because in Finland legally prices with tax and receipt show tax separate.

Is it one tax rate or a local & a "state" rate??

Fwiw, attribute price display information is put together on the store side in includes/modules/YOUR_TEMPLATE/attributes.php. Advise to be cautious about explaining the price(s) and display of each price part. A common issue seen is that the sum of the tax, the base price, and the final price may not line up. While overall this issue has been addressed in say display of the cart total in the most recent ZC, at this individual product level, the values may appear incorrect to a customer.

If tax show separately to receipt. Enough for me.