It will need to be your local MP who takes you case up though, as each MP has to represent their constituents.
Money Saving has received dozens of emails from distraught people whose payments were stopped.
So it's possible Concentrix could still stop your tax credits if it's been investigating you - though it won't be opening any new cases.
If that happens to you and you don't agree with the decision, you should: HMRC's taken over the investigation of all mandatory reconsiderations, including those which have already been launched, and has drafted in an extra 150 staff to help go through a backlog of 2,000 such appeals.
HMRC has taken over all new tax credit checks, and appeals which have already been launched against Concentrix decisions.
However Concentrix is continuing to handle some 200,000 cases which are already open (ie, where Concentrix has notified a person that their tax credit entitlement is being investigated and that they have the standard 30 days to respond).
You can find out who your MP is and how to contact them via the Write To Them website.
A number of MPs including Louise Haigh, Rebecca Long-Bailey and Frank Field have championed the cause of those affected by Concentrix's decisions in the House of Commons, and have urged those affected to get in touch with their MP.
She's recently been diagnosed with postnatal depression and has been put on a high dose of medication. Part-time teacher Emma Henderson and her partner have been without tax credits, which they use to pay for childcare, for six weeks and counting.Despite these hurdles, she managed to get all the requested documents in by Concentrix's deadline, but her money was stopped anyway.She's since been told Concentrix has received her documents but has yet to scan and upload them to their system, leaving her in limbo.We've heard that mandatory reconsiderations are typically dealt with within two to three weeks at the most - HMRC says most cases should be dealt with more quickly than that.You can ask HMRC's Tax Credits Office for updates on your case by phoning it on 03 or using its webchat service.