A lot! Without that experience I don't qualify to even enter the pool. The deal is I left my home country for the US 5 years ago. Got my masters in the US, and came here to Canada for a second masters and right after that I started my PhD. I have a really good education profile but my work experience is very limited. I only have TA/RA work experience from Canada and the US and that one year after my graduation back in Iran is the only work experience I have.http://www.canadavisa.com/canada-immigration-discussion-board/threads/misrepresentation.489323/
You are better off skipping that experience without tax and bank statements as no other documents could prove authenticity like them. Salary slips don't mean much without bank statements.
How much difference is it making to your application?
To be honest I have discussed this in Iranian forums and there are many people applying from Iran through express entry. Not a single person has been asked to provide bank statement or tax return for proof of work experience as far as I know. I am guessing that for Iranian work experience, they rely in organization insurance (which I don't have it as only people who have done the compulsory military service in Iran qualify for it) certificate and contract and pay slips (which I have).
The deal is, I am ok with my application getting rejected, as I already live in Canada and I'm in a great PhD program. However, if I am accused of misrepresentation then that would ruin my life. I am hoping that payslips, contract and reference letter along with the fact that they can call the company I worked for and talk to them will prove I am not presenting fake job documents.