When signing a lease, the tenant is credit checked (UC micro). If the credit check is approved you will get to rent without paying a deposit. The credit check requires a Swedish social security number.
If the credit check is not approved, you will need to pay one month’s deposit. The deposit needs to be paid no later than 10 days after move-in. If you sign the lease closer to move-in than that, you have two days to pay the deposit. You can always see your payments under Leases.