grammatical number - Which is correct, "sales price" or "sale price"?

I have a list of items with their details such as item name, quantity, purchase price, sales price/sale price, etc. What is more correct to write in the heading, sales price or sale price?

Answer

Acoording to Ngram they are both common definitions, but have different meaning as shown below. In your specific case 'sales price' is the correct expression if you are referring to regular, non-discount sales.

Sale price :

• The discounted price of an item from the regular selling price.

Sales price:

• Alternative term for price.

Source: http://www.businessdictionary.com