Will I benefit tax wise by filing as an S Corp for an LLC I formed last fall?

Your electing to be treated as an S-Corp for tax purposes benefits can only be determined with a thorough review of your business operations and income.  It is not an election you just choose to make when it's time to file taxes.  I would suggest seeking out a tax professional in your area to help you with your options.

For an LLC to elect to be treated as an S-Corp you need to file Form 2553.  This needs to be filed no more than 2 months and 15 days after the beginning of the tax year the election is to take effect, or at any time during the tax year preceding the tax year it is to take effect.  There is a late-filing relief that can be requested if you make the election more than 2 months and 15 days after the tax year the election will be in effect, but you need a good reason for the late-filing to be granted the relief.

Once the election is in effect, you as the owner are required to pay yourself a reasonable salary and pay the appropriate payroll taxes for federal, state, and local governments.  You are required to file annual or (more likely) quarterly payroll tax returns with those same governments and issue a W-2 at the end of the year.  See Should I pay myself a salary as an S-corp owner? for more information on this.

Finally, you will file a Form 1120-S and the applicable state business tax return for your tax year that is due March 15 if you file with a calendar year tax year.

[Edited 4/8/23 | 8:19 AM PDT]

@serapio2010