pay into (something)
To contribute money to an account, pool, or some other accumulation of funds. A noun or pronoun can be used between "pay" and "into" to specify the amount of money being paid. All employees pay about 21% of their salaries into the pension fund. I've started paying into a savings account that I only use at Christmas.
pay something into somethingand pay something in
to pay an amount of money into an account. Mary paid forty dollars into my account by mistake. She paid in a lot of money. I have an account here and I want to pay something in.
pay into something
to pay money into an account. I intend to pay into my vacation account until I have enough for a nice vacation. We paid a lot into our savings account this month.