Follow the steps to fill out the MT DoR EST-I online.

1. Click ‘Get Form’ button to obtain the form and open it in the editor.
2. Begin by entering your first name and initial in the designated field. Follow this with your last name.
3. Input your Social Security Number in the provided space, then proceed to enter your spouse's first name and initial, followed by their last name and Social Security Number if applicable.
4. If you are completing this form on behalf of an estate or trust, specify the name of the estate or trust, and include the Federal Employer Identification Number (FEIN).
5. Navigate to Part I - Required Annual Payment. Fill out the required fields by providing your combined tax liability as reported, multiplying it by 90%, and entering your withholding amounts as described.
6. Complete the calculations in Part I to arrive at the required annual payment, ensuring that you stop if your owed interest is less than $500.
7. Proceed to Part II if eligible, and complete the short method by filling in your underpayment amount details.
8. If you have made payments of unequal amounts, transition to Part III for the regular method, filling in each required field, including the corresponding quarterly payment amounts.
9. Complete Part IV if applicable, using the annualized income installment method, and ensure you follow the calculation process accurately based on the provided instructions.
10. After all parts are filled, review your entries for accuracy, then save your changes, download the form, or print it for your records or future submission.

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