Write “2006 IRA contribution” in the memo section of the check. If you are enclosing a payment voucher or coupon provided by the trustee make sure that the correct tax year is marked.
Follow up by checking your next IRA account statement to verify that the contribution was applied to the proper year. If you find that the contribution was applied to the wrong tax year contact the trustee immediately.
IRA trustees must report contributions to the IRS. If your contribution is applied to the wrong tax year (made in April 2007 for 2006 but applied to 2007) you may receive a balance due notice from the IRS 18 months down the road.