Trade Union Subs-Tax Relief Due?

Primary Teacher for 6 years. Just read the articles in papers showing that Revenue have lots of unclaimed tax reliefs. The one that interests me is the tax relief for Trade Union Memberships paid. Am I entitled to any? Thanks

See this Revenue FAQ:

[broken link removed]

and this AAM FAQ:

Are you paying too much tax? A guide to tax credits

You can only backdate tax reclaims by 4 tax years.