Yes, regardless of whether you receive a 1099, you are subject to income taxes on the earned income. This is why so many executor's waive their fees and just take distributions which are not subject to income taxes.
If you were paid over $600 the estate should issue you a 1099 form. If the decedent had a trade or business you have self-employment income and should pay self-employment tax in addition to income tax.
Yes, you did work for the estate and that is income subject to income tax. The estate should send you a 1099 form, but you are required to report the income even if you don't receive the form.
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