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# How do I send my tax return in Luxembourg ?

||| Your tax return must be received by your tax office by 31 December at the latest.
||| Please note: only receipt of your tax return by the Tax Authorities is considered valid. The postmark date is not accepted as proof of timely filing.

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**You must send either form 100 OR form 163, not both!**

[Which form should I send between 100 and 163?](/en/article/which-form-should-i-send-between-100-and-163-1kte7jm/)

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### Form 100 :

Two possibilities:

1) Submit the form and attachments on MyGuichet.lu.
Log in to your myguichet.lu account and submit your tax return and attachments.

[How do I transfer my tax return to myguichet.lu? (ONLY form 100)](/en/article/how-do-i-transfer-my-tax-return-to-myguichetlu-only-form-100-1gxggzq/)

2) Send the form and enclosures by post to your tax office.
Print the PDF and sign the last page after checking the data. The address of the tax office is on the first page, top left.

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### Form 163 :

__Only one option:__

Send the form and attachments by post to your RTS office.
* Print out the PDF and sign on the last page after checking the data. The address of the RTS office is on the first page, top left.