Engage a tax advisor to ensure state and Federal tax compliance.
Typical U.S. corporate tax calendar [in-process]
A permanent establishment (PE) is a fixed place of business that generally gives rise to income or value-added tax liability in a particular jurisdiction.
For a Delaware C-Corp, if key management teams and/or other key operations are located outside of the U.S., it may trigger tax reporting requirements in local countries (specific threshold / evaluation criteria depends on the local jurisdiction).
Discuss with your tax advisor on international tax law compliance and risk assessment.
VAT in UK and EU: Consumption Tax that is applied to all digital/physical goods and services. SaaS companies are to Charge VAT and are categorized as a TBE service according to the EU VAT and UK VAT categories.
To be in compliance with VAT the company needs to do the following items:
Knowing when to Register: When using an invoicing platform, they do have monitoring mechanism to track sales if location of customers are correctly entered and maintained. Once the business is approaching a threshold a notification/warning is sent to the users. Note, even if you are NOT an EU based business, with a US or other location you may still be responsible for collecting VAT and remitting VAT returns.
Below are some high-level guidelines specifically for UK and EU VAT.