The total amount generally cannot exceed $10,500 for the year. Contributions from pay earned in a combat zone will not count against the $10,500 ceiling.
Combat zone contributions will be subject to a different limitation, however, 25% of pay or $35,000, whichever is less.

Contributions to the plan come from "pre-tax" dollars. Servicemembers will pay no federal or state income taxes on contributions or earnings until they're withdrawn.

This year I had less than 10,500 in taxable income thanks to thanks to 8 months of tax free CZTE pay. This will be a recurring pattern for me, so I could just put all my taxable income in the TSP (pre-taxes) and live off my income from the tax free months, and I don't pay taxes for the whole year. That would be fun to do just to say I did it.

Binkley