Is being falsely accused of forgery defamation or libel?

Sue for defamation.

You may sue them for slander, but you have to prove actual $$$ damages. Judges and juries often do not like these type of cases, and you get little verdicts

Libel is a type of defamation. Libel is defamation in written form, and slander is spoken defamation. It sounds like your employer defamed you, because they published a false statement that caused harm to you. However, you should know that the employer can defend against a defamation claim by showing that they had an honest, reasonable belief that you actually committed a forgery.

Libel is a form of defamation and is written. If it is a lie, then yes, you can sue for libel. However, if the boss does not have much money, it may not be worth it.

It could be so you should contact an attorney to find out if you have a viable defamation claim or any other claim against your former employer.

Yes, the publication of a false allegation of a crime is typically regarded as Libel per se. However, defamation is a very nuanced area of the law so there is not enough information to fully answer your question. There are different standards for private individuals, public employees, and public figures. An opinion, if based upon disclosed, non-defamatory facts is generally not actionable. You should invest in hiring an attorney for a detailed conversation about your case. Everything has to be viewed in context. If you are passed over for the employment opportunity, follow up to see if you can find out why that happened.