Shipping Tax

Hi guys,
I`m sorry if this issue has been posted before, I couldn't find anything helpful.

I`m having a frustrating issue regarding shipping tax.
At the moment it's set as following:
- For orders > 500 shipping is free (this works properly)
- For orders < 500 shipping is payable.

My problem is: if i have the order total < 500, the shipping fee is applied as many times as the number of products cheaper than 500 i have in the cart

For example, if I add 10 products that cost 0.20, the shipping tax will be applied 10 times.

I`m getting very frustrated because i've wasted a lot of time trying to find a solution and I simply can't.

Any tips what I should do?

I don't know where the shipping value is taken from. I can't find it.
In my admin settings, the Fixed Rate Shipping value is set to 0. If i change it, it adds up to the existing shipping tax.

I`m using nop 3.40

Any advice would be usefull.
Thank you very much,
Calin

Please clarify "Tax"...  Are you referring to just the shipping rate itself, or a tax on that shipping rate (like a VAT)?

Which Shipping Rate Calculation Methods are you using?  ("Fixed Rate"?)
Be sure that your Products do not have "Ship separately:" checked.

@New York, thank you for your reply.
It seems that the products have a field named "additional shipping cost" and that's the reason for my problems.

Thank you for your time!
Cheers!