I started receiving a monthly annuity from my thrift savings plan in 2017 and I was 55 (almost 56) years old. Do I have to pay the 10% penalty?

[PaulaM · Accepted solution]

If you withdrew from your TSP in the year in which you were 55 or later, you should not be accessed an early withdrawal penalty. 

See excerpt from link below:

'If you receive a TSP withdrawal payment before you reach age 59½, in addition to the regular income tax, you may have to pay an early withdrawal penalty tax equal to 10% of any taxable portion of the payment that is not transferred or rolled over. 

However, if you separate from service during or after the year you reach age 55 (or the year you reach age 50 if you are a public safety employee as defined by section 72(t)(10)(B)(ii) of the Internal Revenue Code), then the 10% early withdrawal penalty tax does not apply.

https://www.tsp.gov/LifeEvents/career/enteringRetirement.html