Question posted in 
I have a collection of items which has a 13% tax. So if you buy $1 in goods, your final charge would be $1.13 because of this tax.
I give users the option to return certain items while purchasing others (imagine returning the keg of beer while buying another).
The problem, however, is that the "return" (where I subtract $X from the checkout) affects the checkout pre tax. So if the total was $100, which is $113 after tax, my current code would deduct $50 pre-tax, which would affect the tax I need to collect.
Is it possible to have the items purchased + tax show in the checkout, and subtract the "returns" after the price plus tax is calculated?
I have looked at this link identifying a similar issue and people claiming they can solve it. The only solution provided by shopify was to pay $2000/month to get access to checkout.liquid where * maybe * I could solve the problem.
2
Answers
Unfortunately, your question is unclear. You have to understand how Shopify works to accomplish certain goals. One, you cannot mess with the pricing of goods or taxes. About the only thing you can offer customers are discount codes.
Anything that gets committed to checkout is out of your control. You cannot adjust anything in the checkout, with the exception being, Plus merchants can indeed script checkout, and even alter the Liquid.
Until you are more clear about what you are attempting, I suggest you ensure that whatever you are doing, the cart is fair game, do as you wish. Have the customer replace one item with another. Submit to checkout. Be done.
Sure, there are cheesy Apps that help fake things financially by using discount codes, but that is often a road to more problems than it is worth.
we have tried this but it did not work for us.
We then ended up disabling the tax altogether
The items were calculated inclusive of tax and we would then provide a tax invoice separately using API