I saw an offer for 100 dollars to file before March 30

[SteamTrain]

It is a "credit', and Requires full service...and you may not actually get anything (probably won't, but that's just my kneejerk opinion)...because it is applied to the cost of the LIVE FULL SERVICE software first...i.e someone prepares your filing for you...but you have to give them all your forms. 

What is the TurboTax Live Full Service $100 back offer? (intuit.com)

[mesquitebean]

Was it this offer that's at the top of the TurboTax main products pages?

"Get $100 back at filing when a Full Service expert does your taxes. Must file by 3/31."

i.e., do you want to enlist one of TurboTax Full Service tax experts to prepare your return?

Prices for typical returns in Full Service currently range from $119 for a very simple Federal return up to $300 or more.

State returns have an additional fee.

[ee-ea]

https://turbotax.intuit.com/lp/bn/4219/?cid=bn_cam_12_891282_386314553_&dclid=CL_X1bykqIQDFQUJaAgdai...