When moving to the Netherlands and trying to avoid double taxation while also deregistering from your country of origin, it's important to understand both the Dutch tax policies and the specific steps for deregistration. Here's a combined overview of what you need to know:

Avoiding Double Taxation
Understanding Tax Treaties: The Netherlands has tax treaties with many countries to prevent double taxation. These treaties outline which country has the right to tax certain types of income, helping you avoid being taxed in both countries on the same income.

Determining Tax Residency: Your tax residency status plays a crucial role. If you have strong social ties to your country of origin (income by real-estate, cash flowing properties, stocks, family business shares etc) this could influence your tax residency status, impacting where you owe taxes at the initial months of relocation. In Europe, tax residency is often determined by the amount of time you spend in a country. Generally, if you stay in a country for more than 183 days (roughly 6 months) in a calendar year, you are considered a tax resident of that country. This means you are liable to pay taxes there on your worldwide income, depending on the country's specific tax laws and any applicable tax treaties. I

Requesting a Certificate of Residence: To affirm your tax residency in the Netherlands, you can request a certificate of residence from the Dutch tax authorities. This is a statement confirming that you are a resident in the Netherlands for tax purposes and subject to income or corporate income tax there. The request can be made via email to woonplaatsverklaring@belastingdienst.nl or send a letter to Postbus 2519, 6401 DA Heerlen.

Deregistering from Your Country of Origin
Providing Proof of New Residence: When deregistering from your country of origin, you typically need to provide proof of your new residence in the Netherlands. This can include a house contract, a recent bill, your employment contract, a BSN certificate, and the certificate of taxation residence from the Dutch tax authorities, just to mention a few.

Legalization and Apostille: The documents provided should be legalized and/or have an Apostille stamp, especially since you are providing copies instead of originals in the case of BSN and certificate or residence. This ensures their validity in your country of origin. That means that before filing and sending them over to your country of origin you need to find a lawyer (notary) to legalize them and/or visit the Court of Appeal (Gerechtshof) to get the Apostille.

Notifying Relevant Organizations: Upon deregistration, it's crucial to notify various organizations like tax authorities and health insurers in both the Netherlands and your country of origin to update your residence status. It's important to check the specific rules and regulations of the country in question, as tax laws can vary significantly. For detailed information, consulting a tax professional or the tax authority in the relevant country is advisable.