How to activate or modify VAT without affecting sales prices in the PrestaShop store

Activate taxes and associate a tax rule with all products

Read this other article to activate taxes and quickly associate a tax rule, either the same for all products, or several different rules, by product groups or categories.

Remove vat from a price incl. tax

This involves recovering old prices inclusive of tax by multiplying them by the ratio (1+TA/100)/(1+TB/100)

If your aim was simply to activate taxes, with sales prices increasing by the amount of the corresponding VAT, that's done, you can stop there.
The next step for you may be to follow our other tutorial for rounding all new prices to psychological prices.

But if you want the prices of all products to remain unchanged, despite the addition of VAT, stay with us. We'll show you how, in just a few clicks, you can change all prices before tax so that the new price before tax + VAT is exactly the same as the old price without VAT.

If you're interested in maths (well, the big word, it's just a rule of three), see below, we'll explain everything.

But let's cut to the chase: to find our old prices, which went from 0% to 20% VAT in step 1, we need to multiply all our sales prices before VAT by 0.833333 (the value of the 1/1.20 ratio). . If the products have variations, you must also multiply all the price impacts before tax by the same value of 0.833333. Complicated? Not at all, it can be done in 4 clicks:

Method 1, the fastest, but blind, with no cancellation possible:

1. Proceed as in step two of the previous tutorial, to use the product modification tool. Enter the value 0.833333 (for our example from 0 to 20%) in the value field.
2. Check that you are on "Value" and not "%".
3. Select "1-Sales price excl. VAT" from the list.
4. Click on the X button to perform the multiplication and confirm the operation. ATTENTION THERE IS NO UNDO with this method.

All prices (including VAT) for all products (without variations) should be restored to their original value, to the nearest cent.

If not, you've made a mistake somewhere. Fortunately, with the calculator, it's always possible to retrace your steps. But in this case, we advise you to try out a single product, using the mass calculator in the product table, which allows you to act on certain products only, as we're going to do with method 2.

Method 2, slower but more reassuring, as it is performed in person, with the possibility of cancellation:

For this method, we need to display all the products to be modified.

1. So start with a very light column selection configuration, with the "Sales price excl. VAT" column to avoid unnecessarily slowing down the operation.
2. Display all products.
3. Select them.
4. Click on the Grouped Actions button.
5. Open the calculator.
6. Enter the same value 0.833333 in the field.
7. Check that the tool is set to "Value".
8. Select "1-Price de vente HT" from the drop-down list.
9. Click on the X button to apply mulitplication.

The results of the calculations are displayed in the table, allowing you to check them before they are saved in the database. If you've made a mistake, you can cancel the operation, which is reassuring at first:

Modify the impact of mass declinations on prices excluding VAT

There's one last step, necessary (but essential) only if your products have variations AND these variations cause prices to vary. In this case, you must also apply the same calculation operation to their price impacts, excluding VAT:

1. As before, create a minimal column configuration for the declination table, with the column Impact on sales price excl. tax.
2. Select all categories, all products (or just those to be modified) and display their variations.
3. Select them all.
4. Click on "Grouped actions"
5. Open the calculator.
6. Enter the same 1/1.20 ratio for the change from 0 to 20%, (i.e. 0.833333) in the value field.
7. Set the selector to "Value".
8. Choose "1-Impacts price excl. tax" from the drop-down list.
9. Click on the X button.
10. Again, the result of each calculation will be displayed on the screen, allowing you to validate or cancel the operation.

How to keep sales prices unchanged when changing VAT rates

When changing from a non-zero rate to another rate, the method is strictly the same: you'll just have to replace the 0.833333 value used in the above examples with the result of a small calculation.

Let TA be the original VAT rate and TB the new rate.

The calculation is as follows: (1+TA/100)/(1+TB/100)

In concrete terms, to convert a product from 19.6% VAT to 21% VAT, for example, while maintaining the same sales price including VAT, the initial price excluding VAT must be multiplied by : (1 +19.6/100) / (1+ 21/100) i.e. 0.988429

Another example: To change from 5.5% to 19.6%, while maintaining the same sales price including VAT, multiply the price excluding VAT by 1.055/1.196, i.e. 0.8821.

Where did the 0.833333 figure come from? It's the result of the same calculation, allowing us to go from an A rate of 0 to a B rate of 20%: 1/1.20.

Need convincing? :

• Let's take a product sold for €110 VAT-free. 
• Adding VAT at 20% gives a new price of €132 before tax.
• Its price excluding VAT has remained unchanged at €110. Multiply it by 0.833333, and you get €91.66663 before tax.
• Of course, the change in price excluding VAT automatically modifies the price including VAT, which is now 91.66663+20%, or 109.99995, rounded up by Merlin to €110 including VAT. We're back on the starting price.

How's your head? Not too bad?