Singapore is introducing Goods and Services Tax (GST) for all imported digital services and this affects Adcash advertisers whose business or personal address is set to Singapore. 

What do Singapore advertisers need to do?
Please make sure that you’ve added your GST Registration Number on your Adcash profile under the billing details (in the "VAT number" field). Once you have added the GST Registration Number to your account, the tax won’t be charged. If you don’t provide a GST Registration number, you will be liable for paying the 7% of GST as of 1st January 2020.

How is Singapore GST calculated? 
If you make a payment of 100$/€ on your account, then the actual balance transferred to your Adcash balance would be 100 minus the GST, which is 100/ (1+7%) = 100/1,07 = $/€93,46

Note: Adcash can't provide tax advice, so please contact your country's tax authority for further guidance and help.