According to your description, the training institution did not provide you with an invoice, but only issued a receipt. In most countries, including China, enterprises are obliged to provide invoices to consumers. So you have the right to ask the training institution to reissue the invoice.

If the training institution refuses to reissue the invoice or intentionally evades taxes, it may constitute tax evasion. Tax evasion is an illegal act, which involves enterprises deliberately concealing or falsely reporting their income to avoid paying taxes. If the training institution is suspected of tax evasion, it can report to the local tax authorities, which will investigate and take corresponding legal measures.

I suggest you communicate with the training institution first and ask them to reissue the invoice. If they refuse or cannot provide the invoice, you can consider reporting it to the tax authorities and providing relevant evidence and details.