For Pay As You Go calls, VAT is charged when you make the call. Call rates will be exactly what you pay for your calls, inclusive of taxes. According to Skype, this makes it easy for you to clearly see how much your calls made from the calling and messaging app cost.
When purchasing Skype Credit, VAT is not charged at the time of purchase. Example: if you buy €10 of Skype Credit, you will only be charged €10. The same applies if you top-up your Skype Credit from within your Skype client on desktop or mobile.
Regarding Auto-recharge, this service (similar to Skype Credit above) automatically tops up your Skype Credit when your balance falls below a certain amount (typically $2 / €2 / £2). VAT is not charged at purchase. Example: if you set your recharge value to €10 of Skype Credit, you will only be charged €10.
If you use your Skype Credit balance to purchase a subscription or have a subscription which uses Skype Credit as a recurring payment, you will be charged 15% VAT for EU residents (8% for Swiss residents) at the point of purchase. VAT is added at the time of the recurring payment.
If you’re utilizing Skype Numbers, VAT is applicable and charged at 15% VAT for EU residents (8% for Swiss residents) at the time of the recurring payment.
Thanks bileshaw for the tip!